Telemetry configurations for downhole communications

ABSTRACT

Systems, apparatus, and methods are described for formatting and for performing data communications between a surface modem and one or more modems located in a logging tool of a bottom hole assembly for use in a wellbore environment.

BACKGROUND

Modern petroleum drilling and production operations demand a greatquantity of information relating to parameters and conditions downhole.Such information may typically include characteristics of the earthformations traversed by the wellbore, along with data relating to thesize and configuration of the borehole itself. The collection ofinformation relating to conditions downhole, which is commonly referredto as “logging,” can be performed by several methods.

For example, in conventional oil well wireline logging, a probe or“sonde” that includes formation sensors may be lowered into a boreholeafter some or all of the well has been drilled, and is used to determinecertain characteristics of the formations traversed by the borehole. Theupper end of the probe or sonde may be attached to a conductive wirelinethat suspends the probe or sonde in the borehole. Power and data orother types of communications may be transmitted to the sensors andinstrumentation in the probe or sonde through the conductive wireline.Similarly, the instrumentation in the sonde may communicate informationto the surface by electrical signals transmitted through the wireline.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure may be better understood by referencingthe accompanying drawings.

FIG. 1 illustrates a schematic diagram of a logging system for aborehole environment according to various embodiments.

FIG. 2A illustrates a graph showing frequency tones utilized in adiscrete-multi-tone telemetry system according to various embodiments.

FIG. 2B illustrates a graph showing manipulation of frequency tonesutilized in a discrete-multi-tone telemetry system according to variousembodiments.

FIG. 2C illustrates a graph showing another manipulation of frequencytones utilized in a discrete-multi-tone telemetry system according tovarious embodiments.

FIG. 2D illustrates a graph showing use of signal-to-noise margin valuesaccording to various embodiments.

FIG. 2E illustrates a set of graphs showing use of signal-to-noisemargin values in a multiplexed data communications format according tovarious embodiments.

FIG. 3 illustrates a flowchart of a method according to variousembodiments.

FIG. 4 illustrates a block diagram of a computer system according tovarious embodiments.

The drawings are provided for the purpose of illustrating exampleembodiments. The scope of the claims and of the disclosure are notnecessarily limited to the systems, apparatus, methods, or techniques,or any arrangements thereof, as illustrated in these figures. In thedrawings and description that follow, like parts may be markedthroughout the specification and drawings with the same or coordinatedreference numerals. The drawing figures are not necessarily to scale.Certain features of the invention may be shown exaggerated in scale orin somewhat schematic form, and some details of conventional elementsmay not be shown in the interest of clarity and conciseness.

DETAILED DESCRIPTION

In the following detailed description of the illustrative embodiments,reference is made to the accompanying drawings that form a part hereof.These embodiments are described in sufficient detail to enable thoseskilled in the art to practice the techniques and methods describedherein, and it is understood that other embodiments may be utilized andthat logical structural, mechanical, electrical, and chemical changesmay be made without departing from the scope of the disclosure. To avoiddetail not necessary to enable those skilled in the art to practice theembodiments described herein, the description may omit certaininformation known to those skilled in the art. The following detaileddescription is, therefore, not to be taken in a limiting sense.

The embodiments described herein relate to systems, apparatus, methods,and techniques that may be used to perform wireline telemetry betweenone or more modems included as part of logging tools configured forperforming logging operations in a borehole environment, and a computersystem, such as a surface modem, configured to be positioned outside theborehole and communicatively linked to the logging tools. In performingthe wireline telemetry, a minimum data rate for both the datacommunications from the modems located downhole to the surface modem(which may be referred to as “uplink data” or “uplink communications”),and data communications from the surface modem to the modem(s) locateddownhole (which may be referred to as “downlink data” or “downlinkcommunications”) may be required. Minimum data rates may define aminimum speed, such as the number of data symbols, that the datacommunications should be capable of transferring per unit of time.

This minimum data rate or rates of data communications may also need tobe performed with a maximum bit rate error defining a maximum number ofbit errors, which may be defined as bit error occurring per unit timesuch as per second, that would be acceptable as part of the datacommunications. Bit errors may be caused for example by switching noisefrom tools and/or power supplies that generate noise signals imposedonto the data transmission medium, such as a conveyance cable orconductor lines, which are being used to transmit and receive the datacommunication signals providing the data communications between thelogging tools and the surface modem. Bit errors may also be caused by areduction of the signal strength being provided as the datacommunications due to transmission media changes caused by temperaturechanges, and other forces being exerted on the transmission mediacarrying the data communication, such as stretch, pressure, and physicaldeformation of the transmission media.

In various embodiment, in order to ensure that the required data ratesfor uplink and downlink data communications can be met while achievingno more than the maximum allowable bit rate error, a minimum level forthe signal-to-noise ratio (SNR) for the data communication signals maybe required. In a data communications system providing telemetry betweena logging tool and a surface modem, a telemetry training procedure maybe performed at initial power up of the logging system in order todetermine the available SNR over the communications lines that willallow the required parameters, such as data rate and bit error rates,for the data communications to be met. In some examples of currenttelemetry systems for logging operations, if the required data rate andthe maximum bit rate error are achievable at the minimum level SNR, thedata communication system may simply allow the logging tool to performthe logging operations, and the data communication to proceed betweenthe modems using the minimum level SNR. In such examples, dummy data maybe sent as part of the data communications to fill the extra availablebandwidth being used for the data communications.

Embodiments of the systems, apparatus, methods, and techniques asfurther described below may be configure to utilize the available toolstring information related to the tools and other instrumentationincluded in a logging tools to transform the extra available bandwidth,and thereby improve the robustness of the data communications, byproviding a higher level of noise immunity and/or to lower the overallpower consumption required to perform the data communications.Embodiment of the systems, apparatus, methods, and techniques as furtherdescribed below may be configured to utilize the available tool stringinformation associated with the logging tools to reallocate data bittransmissions to different frequency channels, as further describedbelow, from frequency channels that are known to susceptible to noise,to frequency channels less susceptible to noise signals, based on typesof logging tools and instrumentation included in the logging tool, andthus allow data communications to proceed using a higher and thus morerobust SNR. In addition, by reallocating the number of bits beingcommunicated on one or more frequency channels being utilized for thedata communications, the overall level of power required to perform thedata communications may be reduced.

FIG. 1 illustrates a schematic diagram of a logging system 100 for aborehole environment according to various embodiments. System 100includes a platform 101 positioned on a surface 102, such as the earth'ssurface, and over a borehole 104 extending into formation 105 belowsurface 102 and extending between borehole walls 108. Platform 101supports a derrick 103 extending above the platform 101, and positionedover a top opening 109 of borehole 104. Platform 101 also supports aworktable 106 that may be configured to be driven by a motor 112, suchas an electrical or a hydraulic motor, configured to rotate theworktable and in turn a drill string (not illustrated in FIG. 1) thatmay extend down into the borehole 104. One or more sections of pipe 107may extend through a central opening in the worktable 106 and throughthe top opening 109 and into borehole 104 to some distance below surface102. Pipe 107 may include a central passageway extending through thepipe that is configured to allow a logging tool, such as logging tool120, to pass through the central passageway of the pipe and be loweredto various depths within borehole 104.

In system 100, a drawworks 110 is suspended from derrick 103 andposition over pipe 107. Drawworks 110 is configured to include amechanism, such as a pulley, that allows a cable, such as conveyance111, to be positioned so as to align with the central passageway of pipe107 and the top opening 109 of borehole 104. Conveyance control system130 is coupled to a proximal portion of conveyance 111, wherein a distalend of conveyance 111 is physically coupled to logging tool 120.Conveyance control system 130 may include a reel and drive mechanismthat is configured to extend out more portions of conveyance 111, and totake in portions of conveyance 111 in a controlled manner, thus loweringand raising, respectively, logging tool 120 within borehole 104.Drawworks 110 is configured to pass extended portions of conveyance 111through the drawworks 110, and thus allow lowing of logging tool 120through pipe 107 and further depth-wise into borehole 104, and to pullretracted portions of conveyance 111 through the drawworks to allowraising the logging tool 120 up through borehole 104 at some controlledrate, and/or to allow logging tool 120 to be withdrawn complete fromborehole 104 through pipe 107. In various embodiments, conveyancecontrol system 130 may be provided as part of a mobile unit 140, such asa truck or a trailer, that may be brought to and removed from the siteas part of the logging operation related to borehole 104.

Logging tool 120 itself may include one or more sensors 121 or otherinstrumentation that may be configured to take measurements related toborehole 104 and/or formation 105 surrounding the borehole while thelogging tool is being lowered and/or is being raised within the borehole104 by control of conveyance 111 using conveyance control system 130.For example, conveyance 111 may comprise a mechanism, such as a cable ora wire, that is configured to support the weight of logging tool 120throughout the movements of logging tool 120 within, into, and out ofborehole 104. In addition, conveyance 111 may include one or moreadditional electrical conductors, such as conductive wires,multi-conductor cable, or a communication bus that is communicativelycoupled to sensors 121, and which may be configured to provide a pathfor communication signals to be transmitted from and received by sensors121.

Additional conductors provided throughout the length of conveyance 111may also include electrical conductor, such as conductive metal wires,configured to provide electrical power, for example electrical powerprovided by conveyance control system 130, to sensor 121 in order topower the electrical circuits and other devices included in the sensorsand/or other instrumentation included in logging tool 120. In variousembodiments, electrical power provided by conveyance control system 130to the logging tool 120 may be used to power one or more electricalpower supplies located within the logging tool that are in turn used topower the sensors 121 and/or other instrumentation included in thelogging tool.

To provide communications between sensors 121 and/or otherinstrumentation located in the logging tool 120 and the surface, in someembodiments conveyance control system 130 may include a surface modem131 communicatively coupled to one or more modems illustrated in system100 as modem 123 and modem(s) 128. For example, sensors 121 may becoupled to a single modem 123 that provides communications between thesensors and/or other devices that are located in logging tool 120 withsurface modem 131. The number of modems that may be included in loggingtool 120 is not limited to any particular number of modems, and mayinclude a single modem such as modem 123, or for example modem 123 andone or more additional modems 128, as illustratively represented bymodem 128 dots 127. Each of the modems included in the logging tool 120may be communicatively coupled to surface modem 131 by one or moreelectrical conductors coupled to the logging tool running throughout thelength of conveyance 111. These electrical conductors may be configuredto provide one-way or two-way data communications between the surfacemodem 131 and one or more of the modems located at or within the loggingtool 120.

Embodiments of modem 131 may include one or more computer processors 133(hereinafter “processor 133”), which may include or be coupled to one ormore computer memories 134 (hereinafter “memory 134”). Processor 133 maybe configured to perform various functions related to the configurationand/or operations of sensors and/or other devices located as part oflogging tool 120, in some embodiments based on programs and/or otherinstructions stored in memory 126. In various embodiments, modem 131 maybe configured to perform any of the functions and provide any of thefeatures as described herein related to configuring the telemetrycommunications between conveyance control system 130 and logging tool120. Embodiments of modem 131 may include a communications interface(hereinafter “interface 132”). Interface 132 may be configured toprovide communications, for example data communications and/or commandtype communications, to and from modem 123 and any other modem(s) thatmay be included in logging tool 120 and coupled to surface modem 131through conveyance 111.

In various embodiments of system 100, modem 131 may be communicativelycoupled to one or more other devices, such as computer system 135 forexample through a wired or wireless communication link 136. Computersystem 135 is not limited to any particular type of computer system, andmay include for example a personal computer, a laptop computer, a mobiledevice such as a smart phone, or any type of electronic device capableof performing electrical communications between the computer system 135and modem 131. In various examples, computer system 135 may be locatedat the site near borehole 104, and may include one or more input/outputdevices, such as a display screen, touch screen, keyboard, and/or acomputer mouse that would allow an operator, such as an engineer or atechnician, to interact with modem 131 and/or logging tool 120. Invarious examples of system 100, modem 131 and/or computer device 135 maybe communicatively coupled to a network 142 through a wired or wirelesscommunication link 141. Network 142 is not limited to any particulartype of network and may include a Local Area Network (LAN) or a WideArea Network (WAN) that provides communicative coupling between modem131 and/or computer system 135 and one or more other devices (not shownin FIG. 1) that may be located off site relative to borehole 104, butallow data and/or control related instructions related to the loggingoperations being or to be performed on borehole 104 to be monitoredand/or otherwise controlled via communications provided over the networkwith modem 131 and/or computer system 135.

Embodiments of modem 123 may include one or more computer processors 125(hereinafter “processor 125”), which may include or be coupled to one ormore computer memories 126 (hereinafter “memory 126”). Processor 125 maybe configured to perform various functions related to the configurationand/or operations of sensors 121 and/or other devices located as part oflogging tool 120, in some embodiments based on programs and/or otherinstructions stored in memory 126. A communications interface(“interface 124”) may be coupled to the processor 125. Interface 124 maybe configured to provide communications, for example datacommunications, to and from modem 123 with other device(s) coupled tomodem 123 through conveyance 111.

In embodiments of system 100 that include more than one modem (asillustratively represented in FIG. 1 by dots 127 and modem 128), each ofthese additional modems may include any of the devices, such as separateprocessor(s), computer memory or memories, and/or interfaces that may beconfigured to perform any of the functions and provide any of thefeatures described above with respect to the corresponding componentsfrom modem 123 and/or as otherwise described for these same orcorresponding devices as provided throughout this disclosure.

Different embodiments of logging tool 120 may comprise variouscombination of sensors, logging tools, and/or power supplies configuredto operate the sensors and logging tools and other instrumentation. Eachof these devices included in logging tool 120 may be defined as part ofa tool string service profile that defines the requirements, such asdata communication and power requirements, that are applicable to thespecific sensors, logging tools, power supplies, and otherinstrumentation included in the particular configuration of the loggingtool 120 to be operated in the performance of a borehole loggingoperation. When initiating a logging operation for example on borehole104 using a logging system such as system 100, an operator, such as anengineer or a technician, may open a logging software application on acomputer system, such as computer system 135.

Computer system 135 may be communicatively coupled to modem 131. Theoperator may then load a tool string service profile associated with theconfiguration of logging tool 120 into the logging software application.Once the operator has loaded the tools string service profile for theparticular logging tool configuration associated with logging tool 120in the logging software application, the requested total telemetry datarate information for the tools string associated with logging tool 120becomes available as part of the data included in the logging softwareapplication. In addition to the total telemetry data rate information,the logging software application may also include a Bit Error Rate (BER)requirement that defines the maximum number of bit errors that areacceptable when transmitting data between the logging tool 120 andsurface modem 131 using the requested total telemetry data rate. Thistotal telemetry data rate information and the BER requirementinformation can be sent from the logging software to the surface modem,such as modem 131 in system 100, via a command generated by the loggingsoftware application.

An important parameter associated with data communications is ameasurement of signal-to-noise ratio (SNR) of the data communications.SNR provides a relative comparison between a signal level of the desiredsignal, such as the signal carrying the data being communicated, and alevel of any noise signal(s) that may be present on the communicationline(s). SNR may be expressed as a measurement in units of decibels(dB). The higher the SNR value, the higher the level the signal power isrelative to the noise power levels. In some examples, a target minimumSNR value may be set as part of a data communication format. In general,as the SNR values goes up (larger data signal strength relative to thenoise signal level present on the signal), the communications becomemore robust, and the number of bit error occurring as part of thecommunication may go down. As SNR values goes down (more noise signalrelative to the data signal strength), the bit error rate in general islikely to increase. In additional, as the data rate or baud rateincreases, the chances of incurring bit errors may also increase. Assuch, there is a balance between accomplishing speed with respect to thedata rates in view of SNR and an acceptable bit error rate whendetermining parameters for telemetry data communications.

In addition to SNR values, other parameters that affect or that may needto be applied to the data communications between a logging tool such aslogging tool 120 and a surface modem such as surface modem 131 mayinclude data rates and bit error rate. Data rates refer to the amount ofdata that may be communicated in a given time period. In general, ahigher data rate requires the transmission of more data bits per unittime compared to a lower or slower data rate. In addition, a bit errorrate may refer to the number of errors that occur with respect to anincorrect bit being transmitted and/or received as part of the datacommunications relative to a total number of bits transferred as part ofthe data communication. For example, if one bit in every one millionbits being communicated as part of a data communication results in animproper data bit being communicated, the bit error rate may be one inone million, or a bit error rate of 10⁻⁶. In embodiments of datacommunication systems, a maximum allowable bit error rate may be set aspart of the requirements for the data communications in addition to aminimum data transmission rate as part of setting the requiredparameters for a given data communications setup.

In various embodiments of system 100, a Discrete Multi-Tone (DMT) methodof formatting the data being communicated between modems, such assurface modem 131 and tool modem 123, may be used. Although embodimentsof these DMT modem-to-modem communications are described with respect toone surface modem, such as modem 131, that is communicating with onetool modem, such as modem 123, these same methods and techniques may beapplied to data communications between more than just two modems, forexample but not limited data communications between a surface modem 131and multiple individual tool modems, such as modems 123-128.

Embodiments of a DMT communications formatting may include determining anumber of data bits assigned to represent a DMT symbol. A symbol mayrepresent any data item, such as a letter, a number, or other type ofsymbol such as a decimal point or a punctuation mark. A DMT symbol mayinclude data bits that represent the particular symbol itself, and oneor more additional bits, such as parity or check bits, that are includedas part of the symbol. The DMT symbols are transmitted over an availablebandwidth by separating the available bandwidth into a plurality offrequency bands, which may be referred to as “tones,” or “frequencychannels,” or “channels,” each channel assigned to a particularfrequency range having a range of contiguous frequencies defining awidth for the channel, and including frequencies uniquely utilized bythat particular channel. For example, embodiments of DMT datacommunications may include separating the available bandwidth into aparticular number of channels, in some examples 256 channels, whichextend over some predefined range of frequencies. Each channel isassigned to a predefined center frequency, and wherein each centerfrequency is separated from adjacent channels by a predeterminedfrequency above and below the center frequency for each channel Standardversions of DMT utilize a fast Fourier transform (FFT) algorithm tomodulate DMT symbols for transmission at a first modem, and todemodulate the DMT symbols at a second modem receiving the DMTtransmission. In various embodiments of DMT data transmission, eachchannel, modulation utilize quadrature amplitude modulation (QAM). Thedata is partitioned into symbols of m bits, and each symbol is processedas one unit both by encoder and decoder.

Using a DMT data communication formatting includes sending “bursts” thatinclude some predefined number of data bits assigned to one or more ofthe plurality of frequency channels that are determined to be“available” to transmits at least one bit of data per burst based on thedetermined SNR assigned for the data transmission, as further describedbelow. Subsequent sets of data “bursts” are used to communicate aplurality of data bits as part of a DMT data communications format. Therate at which that data “bursts” are transmitted, along with the overallnumber of data bits included with each burst, determine an overall datarate for the data communications. As further described below, theavailability of a particular frequency channel to provide datacommunications including at least one bit on a given burst of data, andthe number of bits that may be provided per burst on a particularfrequency channel, may be based at least in part of the signal-to-noiseratio present on that particular frequency channel relative to thedetermined SNR minimum value being utilized for the data transmission.For example, because the data bits used for the data communications areprovided in data bursts, and because the total number of bits that maybe included in any given data burst is affected by the number ofavailable frequency channels and the number of bits that may betransferred per burst on each of the available channels, the maximumoverall data rate for data transmission using the DMT communicationsformatting, for example between surface modem 131 and a tool modem 123,may be dictated by the determined SNR value being used for the datacommunications. The determined SNR value must be set to a SNR value thatallows the data communications to occur while meeting the minimumrequired data rate and while complying with the BER requirement(s) forthe data communications.

In various embodiments of system 100, after surface modem 131 receivesthe information included in the tool string service profile, the surfacemodem may then use the requested telemetry data rate as the target datarate, and based on the target BER requirement, determine a minimumsignal-to-noise ratio, referred to as the “SNR minimum,” that isconfigured to allow for the data transmissions between the logging tool120 and surface modem 131 to be carried out at the required totaltelemetry data rates while not exceeding the maximum BER requirementwith respect to the bit error rate for the transmissions. Any datacommunications between the logging tool 120 and the surface modem 131 istherefore constrained to have a value of no less than the SNR minimumbecause any data transmissions occurring using an SNR value that is lessthan the SNR minimum value may not guarantee that the data transmissionscan be carried out at the minimum required data rate while meeting therequirement for the maximum allowable level for the BER.

In addition to the determined SNR minimum value, each frequency channelhas its own SNR that is estimated for each channel. The number of databits that may be allocated for one burst of data on a particularfrequency channel may be determined by the level of the SNR for thatparticular channel relative to the SNR minimum value, or for example ahigher determined SNR value that may be assigned to the datacommunications. For example, for any frequency channel having a SNR forthat particular channel that is less than the SNR minimum value, thatparticular channel may be considered as being unavailable for allocationof data bits to be transmitted in a data burst. For any frequencychannels having an SNR for that particular channel that is at leastequal to or above the SNR minimum value may be considered as anavailable channel, and one or more data bits may be allocated to betransmitted on that frequency channel as part of a data burst.

The number of data bits that may be allocated to any particularavailable frequency channel in various embodiments is based on thedifference between the estimated SNR value determined for thatparticular channel and an overall determined SNR value being used forthe data transmissions for at least that particular channel, or in someembodiments, for all the available frequency channels. By way ofillustration, for a particular frequency channel X being utilized aspart of data transmission in a DMT data format, for every 3 dB that theestimated SNR for channel X exceeds the determined SNR value selectedfor using in the data transmissions, one data bit may be allocated tothat channel Therefore, if channel X is determined to have an estimatedSNR value that is 9 dB above the determined SNR value selected for thedata communications, three data bits (one data bit each of the 3 dB overdetermined SNR value) may be allocated to channel X.

Based on the total number of available channels, and based on the totalnumber of bits that may be allocated to each of the available channelsusing the estimated SNR for each individual available channel and thedetermined SNR value for the overall data transmissions, a total numberof bits that may be allocated to a give data burst may be made. Infurther view of the number of data bits required to transmit one symbol,and the rate the data bursts may be transmitted, an overall datatransmission rate for the given overall determined SNR value may bedetermined. If the allocated number of bits meets or exceeds therequirements for data rate transmission, and if the determined SNR ishigher than the SNR minimum value, the data transmissions between themodem(s) of logging tool 120 and the surface modem 131 may proceed usingthe higher determined value of the SNR associated with the datatransmission, which is configured to provide data transmission whilemeeting the requirements for the maximum BER.

Embodiments include surface modem 131 and/or modem 123 beginning modemtraining by transmitting a signal including a known symbol at apredetermine signal strength to the respective modem configured toreceive data transmission from the transmitting modem. For example,surface modem 131 may initiate modem training by transmitting a knownsymbol, using a DMT communications format, to modem 123 using apredetermined signal strength on each of the frequency channels assignedfor downlink data transmissions. Upon receiving the transmissionincluding the known symbol, and knowing the predetermined signalstrength, modem 123 determines the received signal strength, and therebydetermines an estimated SNR for downlink data transmission,individually, for each of the frequency channels assigned for downlinkdata transmissions.

Individual estimated SNR values for each frequency channel may bedifferent from other estimated SNR values of other frequency channelsand/or a same value compared to one or more other the frequencychannels, and may be used, as further described below, to determine theallocation of a different and/or a same number of data bits,respectively, to the individual frequency channels. These estimated SNRvalues may then be transmitted to the surface modem for use indetermining a SNR value and for determining data bit allocations to thefrequency channels to be utilized for downlink data communications. In asame or similar manner, modem 123 may transmit to surface modem 131 aknown symbol having a predetermined signal strength over each of thefrequency channels assigned to transmit uplink data communicationsbetween modem 123 and surface modem 131. Upon receiving the transmissionincluding the known symbol, and knowing the predetermined signalstrength, surface modem 131 determines the received signal strength, andthereby determines an estimated SNR for uplink data transmissions,individually, for each of the frequency channels assigned for uplinkdata transmissions.

Once the individual estimated SNR values for the frequency channels havebeen determined, in various embodiments surface modem 131 initiates aniterative process of allocating data bits to the available frequencychannels using one or more proposed SNR values, referred to as the SNRmargin level, to determine the number of data bits that may be allocatedto each available frequency channel at the proposed SNR values, and thusdetermines whether the required data rate(s) may be achieved using adata transmission having a determined SNR that is higher than the SNRminimum value, and thus a more robust data transmission, while provideddata transmission in both the uplink and downlink directions with atleast the minimum required data rate and while meeting the requirementfor a maximum BER.

Once a higher value for a proposed SNR margin value has been determinedthat meets these data transmission requirements, modem training may end,and logging operations may begin including data transmissions betweenthe surface modem 131 and modem 123 using a DMT communications formatand a bit allocation to the available frequency channels based on thedetermined higher value for SNR. In various embodiments, as a result ofconducting the modem training, a determination may be made that therequired data transmission rate meeting the BER requirement may not beachieved based on any of the proposed SNR margin values, or by using theSNR minimum value. In such instances, modem 131 may provide an outputwarning message indicative of the issues with the data transmission,wherein the warning message may be output to a computer system, such ascomputer system 135, and/or output over communication link 141 to one ormore devices communicatively coupled to network 142.

In various embodiments, an operator such as an engineer or a technician,may make adjustments to the system, for example by providinginstructions to system 100 causing the system to place one or moredevices, such as logging tools or power supplies, devices into a silentmode, wherein these devices may be considered to be noisy device(s), andthus reduce the tool string data rate requirement so that the datatransmissions may conform to the data rate, SNR, and BER requirementsfor these data transmissions.

FIGS. 2A-2E represents various embodiments of frequency tones that maybe used in a DMT communication format. Any references to particularfrequencies and to ranges of frequencies as depicted in these figuresare intended as illustrative and non-limiting examples, and otherfrequencies and ranges of frequencies are possible and contemplated foruse with embodiments as described herein, and any equivalents thereof.FIG. 2A illustrates a graph 200 showing various frequency tones utilizedin a DMT communication format according to various embodiments. Graph200 includes a vertical axis 201 representing levels of signal-to-noiseratio (SNR), having increasingly larger values in the upward direction,and a horizontal axis 202 representing frequencies, for example but notlimited to frequencies in in the kilohertz (kHz) range, and whichincrease in frequency when moving along axis 202 to the right. Brackets210, 212, 214, 216, and 218 as shown in graph 200 represent illustrativeand non-limiting respective frequency ranges that may be utilized asfrequency channels for of the data communications included in the DMTcommunication format depicted by graph 200. As illustrated in FIGS.2A-2E, each of the channels is assigned a center frequency, such as X,for channel 1, 2X for channel 2, 3X for channel 3, 4X for channel 4,etc., which is unique to that particular channel. Further, each centerfrequency may be separated from the immediately adjacent frequencychannels by a predefined frequency “Y”. In various embodiments, thechannels being utilized for data communications may be spaced apart fromone another by frequency “Y” and extend over a range of frequencies,such as a range extending from 6 kilohertz to 300 kilohertz. In variousembodiments, the predefined frequency “Y” may conform to a standardfrequency used for standardized DMT communication schemes, which mayutilize a predetermined frequency of separation between channels of4.3125 kilohertz.

Bracket 210 represents a first frequency range, and as shown in graph200, represents frequencies that may not be used or available for datacommunications in the embodiments of the DMT communication format.Bracket 212 represents a second frequency range that may be utilized fortones assigned to frequency channels associated with data downlinkcommunications.

Bracket 214 represents a third range of frequencies that includes aguard band range of frequencies. The guard band may be utilized toprovide assured separation of the tones of the frequency channels beingutilized for downlink communications from the tones of the frequencychannels being utilized for uplink communications. Bracket 216represents a fourth frequency range including frequencies that may beused for tones assigned to frequency channels associated with datauplink communications, and a pilot tone. Bracket 218 representsfrequencies extending above the fourth range of frequencies, andincludes frequencies that may not be used for communications in theembodiments of the DMT communication format.

As illustrated in graph 200, the various frequency ranges represented byat least brackets 212 and 216 may be divided into separate “tones” or“channels” or “frequency channels.” Each frequency channel is centeredaround a separate and different center frequency unique to thatfrequency channel. These individual frequency channels are indicated bynumbers, 1 through 12 and 62 through 64, as shown in graph 200 extendingalong horizontal axis 202. For example, a channel 1 is shown positionedwithin the frequency ranges included below bracket 210. No data bits areallocated to channel 1 as depicted in graph 200. Three separatechannels, numbered 2, 3, and 4, are illustrated in graph 200 within thedata downlink tones including frequency channels indicated by bracket212. Channel 2 (ref. number 220), includes a tone having a centerfrequency at “2X”, with 10 bits allocated to channel 2. Channel 3 (ref.number 221), includes a tone having a center frequency at “3X”, with 11bits allocated to channel 3. Channel 4 (ref. number 222), includes atone having a center frequency at “4X”, with 9 bits allocated to channel4, Channels 3, 2, and 4, as depicted in graph 200, are the frequencychannels dedicated to communicate downlink data, for examplecommunication data being transmitted from a surface modem (e.g., modem131, FIG. 1) to one or more modems (e.g., modems 123, 128, FIG. 1) of alogging tool.

Seven separate frequency channels are illustrated in graph 200 withinthe data uplink tones as generally indicated by bracket 216. Channel 8(ref number 223), includes a tone having a central frequency at “8X”,and having 12 bits allocated to channel 8 Channel 9 (reference number224), includes a tone having a central frequency at “9X”, and having 11bits allocated to channel 9. Channel 10 (ref number 225), includes atone having a central frequency at “10X”, and having 10 bits allocatedto channel 10. Channel 11 (ref number 226), includes a tone having acentral frequency at “11X”, and having 9 bits allocated to channel 11.Channel 62 (ref. number 227), includes a tone having a central frequencyat “62X”, and having 3 bits allocated to channel 62. Channel 63 (refnumber 228), includes a tone having a central frequency at “63X”, andhaving 2 bits allocated to channel 63.

Channels 8 through 12, 62, and 63, as depicted in graph 200, are thefrequency channels dedicated to communicate uplink data, for exampledata communications transmitted from one or more modems (e.g., modems123, 128, FIG. 1) of a logging tool to a surface modem (e.g., modem 131,FIG. 1). Additional channels, such as channels 13 through 61, which areillustratively represented in graph 200 by dots 230, may be includedwithin the frequency range indicated by bracket 216, and in variousembodiments may be utilized as addition channel(s) for uplinkcommunications, but are not depicted in graph 200 for simplicitypurposes only. In addition, the uplink tones included within the rangeof frequencies indicated by bracket 216 may also include a pilot tone,illustrated as channel 12 (ref. number 229), having a central frequencyat “12X”. Additional frequencies, not specifically illustrated in FIG.2A, may be assigned to the downlink tones, but are not depicted in graph200 for simplicity purposes only.

As shown in graph 200, channel 1 has a center frequency positioned tothe left of channel 2, and has a lower center frequency compared tochannel 2, and is not allocated any bits for data communication Channel64, having a center positioned to the right of channel 63, has a highercenter frequency relative to channel 63, and is not allocated any bitsfor data communication. As such, the frequency ranges included inchannels 1 and 64 may act as guard bands below and above, respectivelythe frequency ranges over which the data communications depicted bygraph 200 are supposed to operate within.

In addition, frequency channel 5 having a center frequency at “5X”,frequency channel 6 having a center frequency at “6X”, and frequencychannel 7 having a center frequency at “7X”, include frequencies betweenfrequency channels 4 and 8. Frequency channels 5, 6, and 7, as depictedin graph 200, are not allocated data bits, and are labeled as providinga guard band between the frequencies allocated bit assigned to datadownlink communication and frequency channels allocated data bitsassigned to the upline data communications. These guard band may helpminimize or eliminate cross-talk between the downlink communicationbeing performed by channels 2 through 4 and the uplink communicationthat may be performed using channels 8 through 12, 62, and 63.

As shown in graph 200, each of tones 2 through 4, 8 through 12, 62, and63 includes a signal-to-noise ratio level, indicated by the peak of thefrequency tone, that is specific to that frequency channel, and that isabove the SNR minimum indicated by line 203. As further described above,modem training may include determining an estimated SNR for each of thefrequency channels. The number of bits that are allocated to aparticular frequency channel may be determined based on the amount thatthe estimated SNR value for that particular channel exceeds the SNRminimum level. In some embodiments, one bit may be allocated to a tonefor every 3 dB that the SNR for that tone exceeds the SNR margin level.

Using tone 2 as an example, 10 bits have been allocated to tone 2. Invarious embodiments, the allocation of 10 bits to tone 2 would be basedon tone 2 having an estimated SNR that is 30 dB (3 dB times 10 bits)above the dB level set for the SNR minimum value. As shown in FIG. 2A,each of these frequency channels 2-4, 8-12, 62, and 63 would meet theSNR requirements for a tone that may be used for data transmission ofone or more bits when the SNR for the data transmission by having anestimated SNR level that is at least a minimum level, for example 3 dB,above the level of SNR minimum as indicated by dashed line 203. Inalternative embodiments, one or more of the frequency channels may notbe capable of providing a signal-to-noise ratio level that is above aproposed or minimum SNR level, as further described below with respectto FIG. 2B. In such instances, these channels may not be used for datatransmission, and any bits initially allocated to these tones may bereallocated to other tones that can accommodate an allocation ofadditional bits.

The dashed line 203 represents, in various embodiments, an illustrativeSNR minimum value that, if used for the purpose of bit allocation ofdata bits over a set of available frequency channels, would providedownlink and uplink data communication rates at a desired data rate andmeeting the requirements for maximum BER. However, by setting the SNRvalue at the level illustrated by dashed line 203, the entire capacityof the number of bits that could be allocated to the available frequencychannels may not be utilized, in other words would include excess andunused bandwidth, and the very minimum SNR that could be utilized toachieved this desired data rate and BER requirements would be the SNRthat is utilized.

Embodiment as described throughout the disclosure include systems,apparatus and methods, and techniques that include an iterative processto determine if a higher and a thus more robust SNR could be utilizedfor the data communications, and if so, what higher value for an SNRmight be available for use in a DMT data transmission format to achievethe desired data rate, meet the BER requirements for the datatransmissions, while providing a higher value for the SNR. The highervalue SNR may provide more robust data transmission, and lower theoverall power requirements needed to perform the data transmissions.Arrow 204 and dashed line 205 represent a direction of movement for anda new proposed SNR value that is higher than the SNR value associatedwith SNR minimum and dashed line 203, wherein data communicationsperformed using the new proposed SNR value represented by dashed line205 may provide more robust data communications while still meeting thedata rate and BER requirements for data communication between a surfacemodem and a modem configured to be included as part of a logging tool.

However, as further illustrated in FIG. 2B and as described below,raising the value for the SNR may reduce the overall number of data bitsthat may be included with a data burst being used to transmit the datacommunications, and at some level of the higher SNR value an adequatenumber of data bits per data bursts cannot be allocated to the frequencychannels that remain available at the higher SNR value, and thus therequired data rate for the data transmission can no longer be met.Embodiments of the systems, devices, method and techniques describe inthe disclosure allow for determining if a SNR margin value that ishigher than the SNR minimum value may be utilized to provide datacommunications between two or more modems while meeting the requireddata and BER rates.

FIG. 2B illustrates a graph 250 showing manipulation of data bitallocations based on SNR margin values utilized in a discrete-multi-tonetelemetry system according to various embodiments. Graph 250 includesmany of the same features illustrated and described above with respectto FIG. 2A and graph 200, including a set of data downlink tones (tones2 through 4) separated by a guard band (indicated by bracket 214) and aset of data uplink tones 8 through 12, 62, and 64). In graph 250 asshown in FIG. 2B, the horizontal dashed SNR margin line, now indicatedby reference number 203A in FIG. 2B, is raised vertically relative tovertical axis 201 and above the level of the SNR minimum valueillustrated by dashed line 203. This higher level for dashed line 203Amay be implemented to provide an allocation of data bits to theavailable frequency channels while utilizing a higher SNR margin value,which in turn may provide more robust data communications between thesurface modem and the modem(s) provided in a downhole tool.

However, one or more consequences of raising the SNR margin value to avalue higher than the SNR minimum value may include that one or morefrequency channels previously available for allocation of data bits mayno longer be available for data bit allocations, and one or more of thefrequency channels available may only be available for an allocation ofa smaller number of bits than these channels could have been allocatedusing the SNR minimum value.

As illustrated in graph 250, at an SNR margin value illustrated bydashed line 203A, frequency channel 4 including in the data downlinktones and frequency channels 11, 62, and 63 of the data uplink tones donot provide a channel having an estimated SNR value that is above thehigher SNR margin value indicated by dashed line 203A. As such frequencychannels 4, 11, 62, and 63 are no longer frequency channels that areavailable for allocations of data bits, as illustratively represented bythese tones being shown in graph 200 as dashed lines, and an indicationof zero (0) bits being allocated to each of these same frequencychannels. Any data bit allocations that may have previously beenassigned to these channels when using the SNR minimum value must now bere-allocated, if possible, to some other frequency tone that isavailable and has capacity for these additional bits, for example asrepresented by dashed arrows 251 and 252 illustratively representing therelocation of data bit from frequency channels 62 and 63, respectively.

In addition, one or more of the frequency channels that remain availablefor data bit allocations using the higher SNR margin value representedby dashed line 203A may also have capacity for a smaller total number ofbits that can be allocated to the frequency channel compared to thenumber of bits that could be allocated to these same frequency channelsat the SNR minimum value. Due to the potential loss in the number ofdata bits that may be allocated to the available frequency channels atthe higher SNR margin value, the due to the total number of bits thatmay be allocated across the available frequency channels, raising theSNR value to the higher value above the SNR minimum value may or may notcontinue to allow an allocation of an adequate number of data bits perdata burst that still provides the required data rates using the SNRmargin value.

FIG. 2C illustrates a graph 270 showing another manipulation offrequency tones utilized in a DMT data communications system accordingto various embodiments. Graph 270 includes many of the same featuresillustrated and described above with respect to FIG. 2A and graph 200,including a set of data downlink tones (tones 2 through 4) separated bya guard band (indicated by bracket 214) and a set of data uplink tones(tones 8 through 12, 62, and 64). In graph 270 as shown in FIG. 2C, aplurality of different proposed SNR margin values, illustrativelyrepresented in graph 270 by dashed lines 203A, 203B, 204C, and 203D,having values higher than a SNR minimum value represented by dashed line203, may be tested to determine whether one of these higher proposed SNRmargin values may be utilized for data communications between modems,such as surface modem 131 and tool modem 123, to provide datacommunications that meet the data rate and BER requirements.

In various embodiments, of a DMT telemetry system, the number of bitsthat can be carried at each tone for a desired maximum Bit Error Rate(BER) is given by:

$\begin{matrix}{b_{i} = {\log_{2}\left( {1 + \frac{10^{\frac{SNR_{i}}{10}}}{10^{\frac{\Gamma_{m\; i\; n}}{10}}}} \right)}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

wherein the Γ_(min) is the SNR minimum value that should exist on agiven data transmission to insure the desired BER performance can beobtained, for the data transmission, and wherein SNR_(i) is theestimates of the SNR values of each of the i^(th) tones. The totalnumber of bits carried by the DMT system per DMT symbol is

b _(total)=Σ_(i=1) ^(N) b _(i)  Equation (2)

wherein bi is the number of bits allocated to the i_(th) channel, and Nis the total number of channels to which bits may be allocated.

Based on the b_(total) total number of bits carried per DMT symbol, thetraining data rate (R) may be determined as follows:

$\begin{matrix}{R = \frac{b_{total}}{T_{symbol}}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

wherein T_(symbol) is the total number of symbols to be transmitted perunit time.

Referring to FIG. 1 and system 100 in view of FIG. 2C and graph 270,when an operator loads the tools string service profile in the loggingsoftware, the required total telemetry data rate information for thetools string is available. This information can be sent from loggingsoftware to the surface modem via command. After the modem received thisinformation, the modem will use the requested telemetry data rate as thetarget data rate and use an initially higher SNRs margin value, such asSNR margin value indicated by dashed line 203A, which is some levelabove the SNR minimum value, to start the modem training. The higher SNRmargin values may provide increased robustness and may provide a lowerBER compared to data transmissions that would be performed using the SNRminimum value. The setting of the initially higher SNR margin value,such as the SNR margin value illustratively indicated by dashed line203A, is not limited to a particular value or a particular method ofsetting the value. In some embodiments, the initially higher SNR marginvalue may be set based on some predetermined value, for example but notlimited to a value of 30 dB, added to the SNR minimum value. In variousembodiments, the initially higher SNR margin value may be set based on apercentage, for example but not limited to some percentage, such asthree-hundred percent of the SNR minimum value.

In various embodiments, at the beginning of the logging job, for examplea logging job to log borehole 104 using system 100 and logging tool 120(FIG. 1), an operator creates the tools string service profile usinglogging software. The software will determine the required uplink datarate R_(up) and the required downlink data rate R_(dn) for the loadedtools string. Software send the required data rate information R_(up)and R_(dn) to the surface modem. The surface modem determines therequired number of bits need to be carried over one DMT symbol asb_(target)=R·T_(symbol). Modems start the training to estimate the SNRsover the transmission band for each of the frequency channels (tones)that are allocated for the uplink and the downlink data transmissions.

With the estimated SNRs information determined for each tone, the modemsstart the bit allocation iteration routine to utilizing the initiallyset value (dashed line 203A) for the SNR margin, to determine the numberof bits that can be carried on each of the available frequency tones atthe SNR margin value. As described above, in various embodiments theallocation for a given tone is based on the amount that the estimatedSNR for that tone is above or higher than the proposed SNR margin valuethat is being used for that particular round of data bit allocations.The iteration routine initializes the targeted total number of bits tob_(target) and SNR margin Γ to Γ_(max). For each frequency tone, theiteration routine determine the number of bits can be carried on thistone as:

$\begin{matrix}{b_{i} = {\log_{2}\left( {1 + \frac{10^{\frac{SNR_{i}}{10}}}{10^{\frac{\Gamma}{10}}}} \right)}} & {{Equation}\mspace{14mu}(4)}\end{matrix}$

wherein SNR_(i) is the SNR for i_(th) frequency tone, and F is theproposed SNR margin level being used to determine the bit allocationacross all the tones (see e.g., SNR margin line 203A in graph 270).

After iterating over all the tones, a determination is made as towhether the total number of bits allocated to the frequency tones isgreater than or equal to the target number of bits required for the datatransmission. In instances where the total number of bits is greaterthan the target number of bits, that is, b_(total)≥t_(target), then theiteration process may stop, and communications may proceed using the bitallocation determined be last iteration process and the initially setvalue for the SNR margin. In various embodiments, if the initially setvalue for the SNR margin does provide for allocation of a total numberof data bits to the available frequency channels meeting the data rateand BER requirements, another higher value for SNR margin may be set,and the bit allocation procedure repeated to see if an even higher SNRmargin value may be used that would still allow a bit allocation overthe available frequency channels while also meeting the requirements fordata rate and BER.

Otherwise, in instances where the total number of bits that can beallocated using the initially set SNR margin value indicated by dashedline 203A is less than the target number of bits, that is,b_(total)<t_(target), the iteration process may continue using a smallerproposed SNR margin value, which may be reduced by some predeterminedvalue, and then repeating the bit allocation procedure using theincrementally lowered value for next proposed SNR margin. For example,the set value for a proposed SNR margin may be reduced from the levelindicated by dashed line 203A to a smaller value indicated by dashedline 203B. The amount of the lowering of the SNR margin value betweenthe level indicated by dashed line 203A and dashed line 203B is notlimited to any particular amount, or any particular method fordetermining the amount. In some embodiments, the amount of the reductionof the SNR margin value between the level indicated by dashed line 203Aand dashed line 203B is a predetermined value, such as a predetermineddecibel value. In some embodiments, the amount of reduction in the valueof SNR margin may be dependent on the difference between the initial SNRmargin value (dashed line 203A) and the SNR minimum value (dashed line203), such as a percentage of the difference between these two values.

Using the newly set SNR margin value indicated by dashed line 203B, theprocess of allocating data bits to the available frequency channels asdescribed above is performed. As illustrated, in graph 270, by lowingthe proposed SNR margin value from dashed line 203A to dashed line 203B,frequency channel 4, which was not available for data bit allocationswhen using the higher SNR margin value at dashed line 203A, now has anestimated SNR that exceeds the proposed SNR margin value for dashed line203B. This same change also applies to channel 11. As such, channel 4and/or channel 11 may now have the capacity to have data bits allocatedto these channels. In addition, because of the greater different betweenthe estimated SNR values for each of previously available channels 2, 3,8, 9, and 10, these channels may be able to be allocated additional databits compared to the data bit allocations available for these channelswhen using the higher SNR margin value indicated by dashed line 203A.Due to the lower of the proposed SNR margin level, the number of databits that may be allocated over the now available frequency channels mayhave increased relative to the number of data bits that could beallocated over the available frequency channels when using the proposedSNR margin value indicated by dashed line 203A.

Once the allocation of the data bits over the available frequencychannels using the newly set SNR margin value indicated by dashed line203B has been completed, a determination is made as to whether the totalnumber of bits allocated to the frequency tones is greater than or equalto the target number of bits required for the data transmission. Ininstances where the total number of bits allocated is greater than thetarget number of bits, that is, b_(total)≥t_(target), then the iterationprocess may stop, and communications may proceed using the bitallocation determined be last iteration process and the newly set valuefor the SNR margin indicated by dashed line 203B. In instances where thetotal number of bits that can be allocated using the newly set SNRmargin level indicated by dashed line 203B, is less than the targetnumber of bits, that is, b_(total)<t_(target), the iteration process maycontinue using a smaller SNR margin value such as a proposed SNR marginvalue indicated by dashed line 203C, which may be reduced by somepredetermined value, or by some other method, such as using a percentagevalue, relative to the previously tested proposed SNR margin valueindicated by dashed line 203B.

Now using the newly set SNR margin value indicated by dashed line 203C,the process of allocating data bits to the available frequency channelsbased on the newly set proposed SNR margin value is performed. Once thedata bit allocations over the available frequency channels using thenewly proposed SNR margin value has been completed, a determination ismade as to whether the total number of bits allocated to the frequencytones is greater than or equal to the target number of bits required forthe data transmission suing the newly set SNR margin value. In instanceswhere the total number of bits allocated using the newly set SNR a valuethat is greater than the target number of bits, that is,b_(total)≥t_(target), then the iteration process may stop, andcommunications may proceed using the bit allocation determined be lastiteration process and the newly set value for the SNR margin indicatedby dashed line 203C.

In instances where the total number of bits that can be allocated usingthe newly set SNR margin level indicated by dashed line 203C is lessthan the target number of bits, that is, b_(total)<t_(target), theiteration process may continue using a smaller SNR margin value, such asa SNR margin value indicated by dashed line 203D. The process of bitallocation and making a determination of whether the number of data bitsallocated at the newly proposed SNR margin level indicated by dashedline 203D is greater than or equal to the target rate and can be usedfor data communications, or if the number of allocated data bits is lessthan and cannot be used for the required data communications in a manneras described above with respect to the SNR margins values represented bydashed line 203B and 203C.

The process of allocating bits using the initial and newly set SNRmargin values may continue until the utilized SNR margin allows forallocation of the required number of bits, that is,b_(total)<t_(target), or the utilized SNR margin value reaches theminimum required SNR minimum value (Γ_(min)), and the required number ofdata bits still cannot be allocated over the available frequencychannels. For example, each subsequent round of iterations as describedabove may include reducing the SNR margin by a predetermined amount, andthen performing the next round of iterations. Using the newly reducedSNR margin value, a subsequent round of iterations is performed. Again,if the total number of bits is greater than the target number of bits,that is, b_(total)≥t_(target), then the iteration process may stop, andcommunications may proceed using the bit allocation determined be lastiteration process and the SNR margin value that allowed the requirednumber of data bits to be allocated over the available frequencycannels. Otherwise, in instances where the total number of bits is lessthan the target number of bits, that is, b_(total)<t_(target), theiteration may continue using another new smaller SNR margin that issmaller in value than the SNR margin used in the previous round ofiteration.

The process of iteration using a progressively smaller SNR margin valuesmay continue until either the total number of bits is less than thetarget number of bits can be allocated using the latest SNR marginvalue, or the total number of bits that can be allocated when theproposed SNR margin value has been reduced to the minimum SNR minimumvalue and still will not accommodate the required total number of bitsneeded for the data transmission. The total number of iterations to beperformed, and/or the amount of adjustments in the SNR margin valuesused for each subsequent round of bit allocations is not limited to anyparticular number of rounds of iterations and/or to any particular levelof adjustments made to the SNR margin value between subsequent rounds,and may be determined in some embodiments by a predefined program,and/or by inputs, for example provided by an engineer or a technicianproviding input to the system.

In embodiments wherein the minimum required SNR margin still cannot meetthe requirements for allocating at least the target number of data bits,b_(total), an output may be generated that includes a warning message.The warning message may include a message directed to an operator, suchas an engineer or a technician, to request the operator to put one ormore tools included in the logging tool 120 into a particular mode, suchas a silent mode. Placing one or more of the tools within the toolstring in for example a silent mode may reduce the target number of databits and the overall noise level that is occurring on the datatransmission lines. The reduced target number of data bits and the noiselevel may allow the data transmission to occur while achieving therequired level of bit rate error using the minimum SNR margin setting.

Embodiments of this method of determining if higher values for SNRmargin by be used also utilizes the available tools string informationto transform the extra available bandwidth that is used to transmitdummy data to improve the telemetry robustness and better noiseimmunity. Secondly, by lowering the number of bits sent on each tone,the peak to average power ratio of the transmitted telemetry signal isalso lowered, which will reduce power consumption of downhole telemetrydriver.

Benefits of these methods may provide improved telemetry robustness,better noise immunity and lower power consumptions for datatransmissions between a surface modem and one or more modems included ina downhole tool. As described above, existing telemetry systems usedfixed SNR margin Γ_(min) during the training to determine the achievabledata rate with the estimated SNRs. But in some cases, the achievabledata rate is more than enough for the required data rate to perform thelogging jobs. In these cases, the dummy data are sent to fill in theextra available bandwidth. Embodiments of the methods described in thisdisclosure utilize existing information, i.e. required data rate of thetools string, to transform the extra available bandwidth to improve thetelemetry robustness and better noise immunity. Additional embodimentsof the methods and variations of the techniques as disclosed herein areillustrated and described in further detail as follows.

For example, channels that are being utilized with the availablebandwidth in a DMT scheme include channels ranging from a set of lowerfrequency bands to higher frequency bands. In various embodiments, thechannels utilizing the higher frequency bands may be noisier compared tochannels using the lower frequency bands. In view of this, embodimentsof the systems, apparatus, and method described in this disclosure mayinclude re-allocation of bits or the numb of bits being allocated fromhigher frequency channels to one or more frequency channels utilizing alower frequency band. This re-allocation may allow for a same rate ofdata transmission using less overall power in providing the datacommunications, and/or allow a lowering of the overall bit rate errordue to utilization of the less noisy channels to accomplish the datatransmissions.

FIG. 2D illustrates a graph 280 showing use of signal-to-noise marginvalues according to various embodiments. Graph 280 includes many of thesame features illustrated and described above with respect to FIG. 2Aand graph 200, including a set of data downlink tones (tones 2 through4) separated by a guard band (indicated by bracket 214) and a set ofdata uplink tones (tones 8 through 12, 62, and 64). As illustrated ingraph 280, the data downlink tones 2, 3, and 4 may have data bitallocations made to these frequency channels based on a first SNR marginvalue illustratively represented by dashed line 281. Data uplink tones8, 9, 10, 11, 12, 62, and 63, along with any other tones available underbracket 216, may have data bit allocations made to these frequencychannels based on a second SNR margin value illustratively representedby dashed line 282. The first SNR margin value assigned to the datadownlink tones may be the same or have a different value compared to thesecond SNR margin value assigned to the data uplink tones. In variousembodiments, any of the method and techniques described throughout thedisclosure may be applied separately to the downlink data tones todetermine an assigned SNR margin value for dashed line 281, and appliedseparately to the uplink data tones to determine and assign a value tothe second SNR margin illustratively represented by dashed line 282. Byapplying separate procedures to determine the respective SNR marginvalues for the downlink and the uplink, data tones, a more optimal andmore robust set of data bit allocations may be provided for the overalldata communications format utilizing these assigned SNR margin values.

FIG. 2E illustrates a set of graphs 290 and 292, showing use ofsignal-to-noise margin values in a multiplexed data communicationsformat according to various embodiments. Graphs 290 and 292 include manyof the same features illustrated and described above with respect toFIG. 2A and graph 200, including a set of data tones (tones 2 through 4)and a set of data tones (tones 8 through 12, 62, and 64). As illustratedin graph 290, all of the frequency channels included under both bracket212 and bracket 216 are designated as “data uplink tones” and areconfigured for data bit allocations including data bits to becommunicated as part of the uplink data communications. In variousembodiments, because all of the tones in graph 290 are being used as“data uplink tones,” a guard band separating the tones included underbracket 212 and 216 may not be required or utilized. In variousembodiments, the frequencies falling between the frequencies indicatedby bracket 212 and 216 may be used as additional tones having data bitsassigned to these tones. Graph 290 further illustrates a SNR marginvalue, illustratively represented by dashed line 291, which may beutilized to determine the data bit allocations used to configure thefrequency channels represented in graph 290 as part of an uplink datacommunications format. As illustrated in graph 292, all of the frequencychannels included under both bracket 212 and bracket 216 are designatedas “data downlink tones” and are configured for data bit allocationsincluding data bits to be communicated as part of the downlink datacommunications. In various embodiments, because all of the tones ingraph 292 are being used as “data downlink tones,” a guard bandseparating the tones included under bracket 212 and 216 in graph 292 maynot be required or utilized. In various embodiments, the frequenciesfalling between the frequencies indicated by bracket 212 and 216 ingraph 292 may be used as additional tones having data bits assigned tothese tones. Graph 292 further illustrates a SNR margin value,illustratively represented by dashed line 293, which may be utilized todetermine the data bit allocations used to configure the frequencychannels represented in graph 290 as part of a downlink datacommunications format.

In various embodiment, the data formatting illustrated in graph 290 maybe provided as a first data burst, and multiplexed with the dataformatting illustrated in graph 292 as a second data burst transmittedas a different time from a time when the first data burst istransmitted. The SNR margin value represented in graph 290 as dashedline 291 may be set using any of the methods and techniques describedherein and any equivalent thereof, and may be a different value set forthe SNR margin value represented in graph 292 as dashed line 293, whichmay also be determined using any of the methods and techniques describedherein, and any equivalents thereof. In various embodiments, multiplexeddata transmissions based on a configuration of the frequency channelssuch as but not limited to the frequency channels illustrated in graphs290 and 292, respectively, may allow for more robust data transmissionby utilizing a higher and optimal or near optimal SNR margin value foreach of these respective uplink and downlink data transmissions. Byapplying only uplink or downlink data bit allocation to each of theserespective data burst configurations, a data format that is able toutilize a higher SNR margin value may be achievable comparted to an dataconfiguration that utilizes both uplink and downlink bit allocation on asame data burst.

FIG. 3 illustrates a flowchart of a method 300 according to variousembodiments. The flowchart is provided as an aid to understanding theillustrations, and is not to be used to limit scope of the claims. Theflowchart depict example operations that may vary within the scope ofthe claims. Additional operations may be performed; fewer operations maybe performed; the operations may be performed in parallel; and theoperations may be performed in a different order. It will be understoodthat each block of the flowchart illustrations and/or block diagrams,and combinations of blocks in the flowchart illustrations and/or blockdiagrams, may be implemented by program code. The program code may beprovided to one or more processors of a modem, a general purposecomputer, a special purpose computer, or other programmable machines orapparatus.

In the description below, various operations included in method 300 aredescribed as being performed by one or more processors (hereinafter “theprocessor”) that may be included as part of surface modem 131 as shownin FIG. 1. However, embodiments of method 300 are not limited to havingthe various operations and method steps being performed by the processorincluded as part of surface modem 131. Portions of or all of theoperations and methods steps may be performed in part or wholly by otherprocessors, such as but not limited to processors located in modemsincluded in a logging tool, such as processors located in tool modems123 and/or additional modems, such as modem 128 as illustrated anddescribed with respect to FIG. 1. In various embodiments, portions of orall of the operations and methods steps included in method 300 may beperformed in part or wholly by other processors, such as but not limitedto processors located in a computer system coupled to modem 131, such ascomputer system 135 as illustrated and described with respect to FIG. 1.

Method 300 includes the processor receiving a tool string serviceprofile (block 302). The tool string service profile may include avariety of information including the type and number of sensors includedin the logging tool, the types and parameters associated with one ormore power supplies included in the logging tool to power the sensorsand tools, and to power telemetry communications to and from the loggingtool. In some embodiments, the tool string service profile is based onthe configuration and operating parameters of an actual tool string thatis being prepared for a logging operation in a borehole. In otherembodiments, the tool string service profile is based on a proposedconfiguration for a tool string that is being considered and reviewedfor possible use in a logging operation.

Based on the received tool string service profile, method 300 includesthe processor determining one or more data rates for the tool string(block 304). In various embodiments, determining the one or more datarates includes determining a required uplink data rate forcommunications originating from the logging tool that are to betransmitted to a surface modem through a wired communication link, anddetermining a required downlink data rate for communications originatingfrom the surface modem through the wired communication link to thelogging tool. In various embodiments, the data rate or data rates areincluded in the data provided with the tool string service profile. Thedata provided by the tool string service profile may include a value fora maximum BER that needs to be conformed to when the telecommunicationsare being provided at the target data rate.

Based on the determined one or more data rates, method 300 includes theprocessor determining a target total number of bits, b_target, and setsa value for an initial SNR margin (block 306). The initial value set forthe SNR margin is a value that is greater than a minimum SNR, referredto as SNR minimum. The SNR minimum value represents a minimum SNR thatcan be tolerated while still guaranteeing an acceptable BER during thetelemetry data transmission to be performed between modems as part of alogging procedure. For example, if a SNR minimum value of 18 dB has beendetermined for the value for an acceptable maximum BER, the initial SNRmargin value may be set to 30 dB.

Method 300 includes the processor beginning training to estimate theindividual SNRs over the transmission band for each of the frequencychannels that are available for allocation of data bits (block 308). Theestimated SNR for each individual frequency channel may be differentfrom the estimated SNR for other frequency channels that are consideredavailable channels for data communication. In various embodiments, theestimated SNR for an individual frequency channel may be determined asfollows. Assuming that the data communications using the frequencychannels is to occur between a surface modem and a downhole modem, theprocess begins by sending a known training signal, for example includingdata representing a known DMT symbol, between surface modem and downholemodem. When the downhole modem receives the known training signal S_r,it is equal to S_r=S_t+Noise, wherein S_t is the known training signaland “Noise” is the signal strength of any noise signals received withthe known training signal. The Noise can be estimated byNoise_estimate=S_r−S_t, and then the SNR can be determined by theformula SNR=10*log 10(S_t{circumflex over( )}2/Noise_estimate{circumflex over ( )}2). SNR is the signal power tonoise power ratio for the frequency channel used to transmit the knowntraining signal. This process may be repeated for each of the availablefrequency channels, and thereby establishing an estimated SNR for eachindividual frequency channel A similar process may be repeated foruplink data communications, wherein the known training signal istransmitted from the downhole modem to the surface modem, and the SNRfor each of the frequency channels intended for uplink communicationsmay be estimated.

Using the estimated SNRS for each individual frequency channels, method300 includes the processor allocating the number of bits that can beallocated for data transmission on each tone (available frequencychannels) based on the estimated SNR determined for that tone and thecurrent value set for the SNR margin, (block 310). For the first roundof determining bit allocations, the current value for the SNR marginwould be the initial value set for the SNR margin. For any tones havingan estimated SNR value that is below the current SNR margin value, thesetones are indicated as being “unavailable” for bits to be allocated tothat tone. For any tones have an estimated SNR value greater than thecurrent SNR margin value, a determination is made as to how many bitsmay be allocated to that tone. In various embodiments, the number ofbits that may be allocated to a particular tone is determined by thedifferent in the values for the estimated SNR for a that particular toneand the current value of the SNR margin. In various embodiments,Equation 4 as provided above may be used to determine the number of bitsthat may be allocated to a particular frequency channel.

In some embodiments, a difference value per bit may determine theoverall number of bits that may be allocated to that tone. By way ofexample, a current value for the SNR margin may have a value of 30 dB,and an estimated SNR for a particular frequency channel may be 39 dB.Using a difference value of 1 bit per every 3 dB difference in valuebetween the SNR margin and the estimated SNR for the particularfrequency channel, that frequency channel may be allocated to have threedata bits based on the 9 dB difference between the 39 dB value for theestimated SNR and the 30 dB value currently assigned to the SNR margin.Because each frequency channel available for bit allocations may have adifferent estimated SNR value, the number of bits allocated to eachfrequency channel may vary based on the difference between the estimatedSNR for each channel and the current value set for the SNR margin.

After the allocation of the total number of bits that can be carried oneach available tone based on the current SNR margin value for therespective tones is completed, method 300 includes determining whetherthe total number of bits allocated over the available frequency tones isgreater than or equal to the target total number of bits b_target (block312). If the total number of bits allocated over the tones included inthe communication bandwidth is greater than or equal to b_target (“YES”arrow extending from block 312), that indicates that the required numberof bits to be transmitted can be allocated over the available tones atthe designated SNR margin for each tone and still meet the required biterror rate. In such cases, method 300 may proceed to set the data ratesfor any logging operations with the rate trained data rate (block 314).Any logging operations then performed may include telemetrycommunication between the logging tool and a surface modem using the setdata rates between the modems and the bit allocated determined for thelatest SNR margin valued used to allocate the bits.

In the alternative, if the total number of bits allocated over the tonesincluded in the communication bandwidth at block 312 is not greater thanor equal to b_target (“NO” arrow extending from block 312), thatindicates that the required number of bits to be transmitted cannot beallocated over the available tones at the designated SNR margin for eachtone and still meet the required bit error rate. In such cases, method300 proceeds to block 320.

At block 320, method 300 includes the processor determining whether thecurrent value for the SNR margin can be lowered without going below theSNR minimum value. In other words, a determination is made as to whetherthe current value for the SNR margin Γ is greater than the predeterminedvalue for SNR minimum Γ_(min). If the current value for SNR margin isgreater than Γ_(min) (“YES” arrow extending from block 316), method 300progresses to block 322. At block 322, the processor determines a newvalue for SNR margin. The new value for the SNR margin may be determinedby lowering the current and previously tested SNR margin value by apredetermined amount. For example, if the current SNR margin is set to avalue of 18 dB, the process may lower this value by a fixed amount, suchas 0.5 to reduce the SNR margin to 17.5 db. The amount that the currentSNR margin value is reduced by is not fixed to any particular value, andmay be a non-zero value greater than, equal to, or less than 1.

In some embodiments, the amount that the SNR margin is reduced by is notbased on a fixed or predetermined amount, but may instead be determinedbased on some other technique. For example, the amount of reduction ofthe SNR margin value that is to be applied to the current value for theSNR margin may be based on the relative different between the currentSNR margin and the SNR minimum value Γ_(min). For example, the SNRadjustment made at block 322 may include setting the new SNR marginvalue to some percentage value of the different between the current SNRmargin value and the SNR minimum value Γ_(min) value. For example, theamount of adjustment made to the current SNR value to set the new SNRmargin value may be set to fifty percent of the difference between thecurrent SNR value and the Γ_(min) value.

Using this technique, the first time block 322 is executed as part ofmethod 300, the amount of adjustment made the SNR margin value may belarger than any of the subsequent adjustments to the SNR margin value,and thus the series of adjustments to the SNR margin values may bearranged to proceed using a series of non-linear or non-equal leveladjustments relative to prior and/or for subsequent SNR margin valueadjustments. In various embodiments, any adjustment to the current SNRmargin value that would reduce the SNR margin value below the Γ_(min)value will not be allowed, and SNR margin values may be set to Γ_(min)in such instances before proceeding with the next step of method 300.Once a determination has been made at block 320 that a new lower currentvalue for SNR margin value can be made, method 300 may proceed to block322, wherein the processor sets the SNR margin value to the new smallerSNR margin value, and proceeds back to block 310.

At block 310, the processor again initiates the process used todetermine the number of bits that can be allocated to each availabletone based on the estimated SNR determined for that tone and the currentsetting for the SNR margin value. Once the total number of bits havebeen allocated using the newly assigned SNR margin value, method 300proceeds to block 312, wherein the processor determines if the totalnumber of allocated bits allocated by the latest allocation processusing the current SNR margin value is greater than or equal to b_target.If the total number of bits allocated in the latest round of bitallocations is greater than or equal to b_target, method 300 may proceedto block 314, including setting data rates at the latest used values forSNR margin.

Returning to block 312, if the processor determines that the totalnumber of bits allocated in the latest assigned value for SNR margin isnot greater than or equal to b_target, the method may again return toblock 320, to determine if the current SNR is greater than SNR min, andto proceed with another adjustment the SNR margin value if such anadjustment can be made without lowering the SNR margin to a value belowΓ_(min). This cycle of allocating bits based on a current value of SNRmargin, determining if the total number of allocated bits is greaterthan or equal to b_target, and if not, adjusting the value SNR margin tosome lower value if such an adjustment can be made relative to the SNRminimum value may be repeated any number of times until either the totalnumber of allocated bits at the current SNR margin value is greater thanor equal to b_target, or the SNR margin value has reached the SNRminimum value Γ_(min), and the total number of bit that can be allocatedusing the Γ_(min) SNR margin value is still not greater than or equal tob_target.

When the total number of bits that can be allocated using a SNR marginvalue that is equal to the SNR minimum value Γ_(min) is still not equalto or greater than b_target, method 300 may proceed from block 320 toblock 324. At block 324, the processor in method 300 issues a warningoutput. The warning output may include an indication that the totalnumber of bits that may be allocated to the available frequency channelsusing the SNR minimum value will not accommodate the b_target requirednumber of bits. In various embodiments, the warning output may includeinformation related to this situation, such as a total number of bitsallocated using the latest SNR margin value, the Γ_(min), value, alisting of the estimated SNR values for each of the frequency channels,and/or the latest setting for the data training rates. The warning mayfor example be provided as an output that may be visible to an operator,for example as a message provided on a display of a computer system suchas computer system 135 (FIG. 1).

In various embodiments of method 300, following issuance of a warningindication at block 324, the processor may provide output instructionsthat place one or more tools or other instruments included in thelogging tool into an OFF mode, or into a silent mode of some type. Whenin the off or silent mode, the particular logging tool in that state maynot be transmitting or receiving data as part of the logging operation,and thus does not contribute to the data bit load associated with thedata transmissions between the logging tool and the surface modem,and/or does not contribute to noise that may be generated in instanceswhere the deice or devices now in the off or silent mode were insteadoperational. In various embodiments, the decision as to which tool ortools are to be placed in the off or silent mode may be based oninformation already stored in a memory coupled to the processor, and mayoccur automatically upon generation of the output warning indication. Invarious embodiments, the decision as to which tool or tools are to beplaced in the off or silent mode may be based, in part or in whole, oninputs provided by an operation and received by the processor.

In various embodiments, once one or more of the logging tools are placein the off or silent mode, method 300 may proceed to block 328, whereinthe logging operation is performed using the last trained data rate andwith the one or more tools remaining in the off or silent mode. Invarious embodiments, adjustments to the tools turned off or placed insilent mode may be considered as re-creating a new tool string serviceprofile from the originally downloaded tool string service profile. Insuch embodiments, the new tool string service profile may be received,as described above for block 302, wherein method 300 proceeds asdescribed above to perform the steps and operations to determine a newset of bit allocations and a new value for a SNR margin that may beusable for telemetry data communication between a surface modem and adownhole modem based on the new tool string service profile.

Variations to the operations described above with respect to method 300are possible and are contemplated for use in setting up the datacommunications between a surface modem, such as surface modem 131, andone or more tool modems, such as tool modem 123. In some embodiments, ifthe initial first round of bit allocations performed with the initiallyset value for the SNR margin results in the total number of bitsallocated to the available frequency channels being equal to or greaterthan b_target, method 300 may include raising the value of SNR margin toone or more larger values, and performing the bit allocation processusing each of these one or more larger values to determine if an evenlarger value for SNR margin compared to the initially set SNR marginvalue could result in a bit allocation that would allow a number of bitsequal to or greater than b_target to be allocated over the availablefrequency channels. If such a larger SNR margin value would stillprovide a bit allocation including a numb of bits greater than or equalto b_target, logging operations may proceed as described at block 314,but using the higher SNR margin value.

In various embodiments, in the process of testing a progressivelysmaller SNR margin value as described above, if a given SNR margin valueresults in a bit allocation having a number of bits allocated over theavailable frequency channels that is greater than b_target, embodimentsof method 300 may include raising the SNR margin value upward to alarger margin value that is between the last SNR margin value tested andthe previously used SNR margin value that did not allow for a number ofbits to be allocated over the available frequency channels that wasgreater than or equal to b_target. If this raised SNR margin valueresults in a bit allocation that includes a number of bit allocatedequal to b_target, logging operations (block 314) may proceed using theraised SNR margin value. If this raised SNR margin value results in abit allocation that included a number of bis allocated that is greaterthan b_target, method 300 may include again raising the value of SNRmargin to a new and larger SNR margin value, and again determining ifthe number of bits that may be allocated using the new and larger SNRmargin value is equal to or greater than b_target. By raising the SNRmargin value and testing the bit allocations at one or more of theraised SNR margin values, method 300 may determine a SNR margin valuethat optimizes the signal strength of the data commutations while stillmeeting the data rate and BER requirements. In doing so, method 300 maydetermine an optimal or near optimal SNR margin value, and thus an morerobust DMT data communications format for use in a system, such as butnot limited to system 100 of FIG. 1.

In various embodiments of method 300, the process of determining a SNRmargin value that may be used for DMT data communications may includeseparately determining a SNR margin value for the uplink datacommunications and for the downlink data communications. For example,the process described above and any variations thereof may be performedfor a set of frequency channels designated for the uplink datacommunications to determine a SNR margin value that may be applied tobit allocations utilized for the uplink data communication, andperformed separately on a different set of frequency channels designatedfor the downlink data communications. These separate processes mayresult in assigning a first SNR margin value for the uplink datacommunications that is the same or that is different from a second SNRmargin value assigned for the downlink data communications. In variousembodiments, wherein one or more same frequency channels are utilized ina multiplexed data burst arrangement to provide both uplink and downlinkdata communication, method 300 may be utilized to determine separatelySNR margin values, which may be the same or different SNR margin values,for use during each of the individual multiplexed data bursts.

FIG. 4 illustrates a block diagram of an example computing system 400that may be employed to practice the concepts, methods, and techniquesdisclosed herein, and variations thereof. The computing system 400includes a plurality of components of the system that are in electricalcommunication with each other, in some examples using a bus 403. Thecomputing system 400 may include any suitable computer, controller, ordata processing apparatus capable of being programmed to carry out themethod and apparatus as further described herein. In various examples,one or more components illustrated and described with respect tocomputing system 400 may be included in or as a component of modem 131,and/or any of modems 123 to 128 as illustrated and described withrespect to FIG. 1, and may include any of the features and/or performany of the function described with respect to these modems, includingany of the methods and techniques described throughout this disclosure,and any equivalents thereof.

Referring back to FIG. 4, computer system 400 may be a general-purposecomputer, or a computing device packaged to withstand the downholeenvironment, including temperature sand shock stresses that may beencountered in a borehole. In various embodiments, computer system 400includes a processor 401 (possibly including multiple processors,multiple cores, multiple nodes, and/or implementing multi-threading,etc.). The computer system includes memory 407. The memory 407 may besystem memory (e.g., one or more of cache, SRAM, DRAM, zero capacitorRAM, Twin Transistor RAM, eDRAM, EDO RAM, DDR RAM, EEPROM, NRAM, RRAM,SONOS, PRAM, etc.) or any one or more of the possible realizations ofmachine-readable media. The computer system also includes the bus 403(e.g., PCI, ISA, PCI-Express, HyperTransport® bus, InfiniBand® bus,NuBus, etc.) and a network interface 405 (e.g., a Fiber Channelinterface, an Ethernet interface, an internet small computer systeminterface, SONET interface, wireless interface, etc.).

The computer may also include an image processor 411 and a controller415. The controller 415 may control the different operations that canoccur in the response inputs from sensors 419 and/or calculations basedon inputs from sensors 419 (such as sensors included in logging tool120, FIG. 1) using any of the techniques described herein, and anyequivalents thereof. For example, the controller 415 can receive and/orprocess signal received from one or more sensors 419 included in loggingtoo. In various embodiments, controller 415, based on instructions fromprocessor 401, may control one or more logging tools, for example toplace one or more of the logging tools into an off mode or a silentmode.

Any one of the previously described functionalities may be partially (orentirely) implemented in hardware and/or on the processor 401. Forexample, the functionality may be implemented with an applicationspecific integrated circuit, in logic implemented in the processor 401,in a co-processor on a peripheral device or card, etc. Further,realizations may include fewer or additional components not illustratedin FIG. 4 (e.g., video cards, audio cards, additional networkinterfaces, peripheral devices, etc.). As illustrated in FIG. 4, theprocessor 401 and the network interface 405 are coupled to the bus 403.Although illustrated as also being coupled to the bus 403, the memory407 may be coupled to the processor 401 only, or both processor 401 andbus 403.

Controller 415 may be coupled to sensors 419 and to logging toolscontrols 421 using any type of wired or wireless connection(s), and mayreceive data, such as measurement data, obtained by sensors 419 Sensors419 may include any of the sensors associated with a wellboreenvironment, including sensors and logging tools such as a High-FidelityBorehole Imager configured provide information related tomicro-resistivity associated with the borehole environment. Controller415 may include circuitry, such as analog-to-digital (A/D) convertersand buffers that allow controller 415 to receive electrical signalsdirectly from one or more of sensors 419.

Processor 401 may be configured to perform one or more of the datatelemetry communication functions as described throughout thisdisclosure, and any equivalents thereof. For example, processor 401 maybe configured to perform program steps that when perform, provide any ofthe features described above with respect to configuring datacommunications between a logging tool and a surface modem. In addition,processor 401 may be configured to control network interface in order toprovide data communications to and/or from computing system 400 usingany of the methods and techniques for configuring the data transmissionsas described throughout this disclosure, and any equivalents thereof.

With respect to computing system 400, basic features may easily besubstituted for improved hardware or firmware arrangements as they aredeveloped. In some examples, memory 407 includes non-volatile memory andcan be a hard disk or other types of computer readable media which canstore data that are accessible by a computer, such as magneticcassettes, flash memory cards, solid state memory devices, digitalversatile disks (DVDs), cartridges, RAM, ROM, a cable containing a bitstream, and hybrids thereof.

It will be understood that one or more blocks of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented byprogram code. The program code may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable machine or apparatus. As will be appreciated, aspects ofthe disclosure may be embodied as a system, method or programcode/instructions stored in one or more machine-readable media.Accordingly, aspects may take the form of hardware, software (includingfirmware, resident software, micro-code, etc.), or a combination ofsoftware and hardware aspects that may all generally be referred toherein as a “circuit,” “module” or “system.” The functionality presentedas individual modules/units in the example illustrations can beorganized differently in accordance with any one of platform (operatingsystem and/or hardware), application ecosystem, interfaces, programmerpreferences, programming language, administrator preferences, etc.

Computer program code for carrying out operations for aspects of thedisclosure may be written in any combination of one or more programminglanguages, including an object oriented programming language such as theJava® programming language, C++ or the like; a dynamic programminglanguage such as Python; a scripting language such as Perl programminglanguage or PowerShell script language; and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on astand-alone machine, may execute in a distributed manner across multiplemachines, and may execute on one machine while providing results and oraccepting input on another machine. While depicted as a computing system400 or as a general purpose computer, some embodiments can be any typeof device or apparatus to perform operations described herein.

Aspects of the disclosure may be embodied as a system, method or programcode/instructions stored in one or more machine-readable media.Accordingly, aspects may take the form of hardware, software (includingfirmware, resident software, micro-code, etc.), or a combination ofsoftware and hardware aspects that may all generally be referred toherein as a “circuit,” “module” or “system.” The functionality presentedas individual modules/units in the example illustrations can beorganized differently in accordance with any one of platform (operatingsystem and/or hardware), application ecosystem, interfaces, programmerpreferences, programming language, administrator preferences, etc.

Any combination of one or more machine readable medium(s) may beutilized. The machine readable medium may be a machine readable signalmedium or a machine readable storage medium. A machine readable storagemedium may be, for example, but not limited to, a system, apparatus, ordevice, that employs any one of or combination of electronic, magnetic,optical, electromagnetic, infrared, or semiconductor technology to storeprogram code. More specific examples (a non-exhaustive list) of themachine readable storage medium would include the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a portable compact disc read-only memory (CD-ROM), anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, a machinereadable storage medium may be any tangible medium that can contain, orstore a program for use by or in connection with an instructionexecution system, apparatus, or device. A machine readable storagemedium is not a machine readable signal medium.

A machine readable signal medium, including non-transitory computerreadable mediums, may include a propagated data signal with machinereadable program code embodied therein, for example, in baseband or aspart of a carrier wave. Such a propagated signal may take any of avariety of forms, including, but not limited to, electro-magnetic,optical, or any suitable combination thereof. A machine readable signalmedium may be any machine readable medium that is not a machine readablestorage medium and that can communicate, propagate, or transport aprogram for use by or in connection with an instruction executionsystem, apparatus, or device.

Program code embodied on a machine readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thedisclosure may be written in any combination of one or more programminglanguages, including an object oriented programming language such as theJava® programming language, C++ or the like; a dynamic programminglanguage such as Python; a scripting language such as Perl programminglanguage or PowerShell script language; and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on astand-alone machine, may execute in a distributed manner across multiplemachines, and may execute on one machine while providing results and oraccepting input on another machine.

The program code/instructions may also be stored in a machine readablemedium that can direct a machine to function in a particular manner,such that the instructions stored in the machine readable medium producean article of manufacture including instructions which implement thefunction/act specified in the flowchart and/or block diagram block orblocks.

While the aspects of the disclosure are described with reference tovarious implementations and exploitations, it will be understood thatthese aspects are illustrative and that the scope of the claims is notlimited to them. Plural instances may be provided for components,operations or structures described herein as a single instance. Forexample, reference to “a processor” in the disclosure and in the claimsis not limited to use of a single processor along, and may include aplurality of processors operating in some manner to perform thefunction(s) and features ascribed to the processor. Finally, boundariesbetween various components, operations and data stores are somewhatarbitrary, and particular operations are illustrated in the context ofspecific illustrative configurations. Other allocations of functionalityare envisioned and may fall within the scope of the disclosure. Ingeneral, structures and functionality presented as separate componentsin the example configurations may be implemented as a combined structureor component. Similarly, structures and functionality presented as asingle component may be implemented as separate components. These andother variations, modifications, additions, and improvements may fallwithin the scope of the disclosure.

Use of the phrase “at least one of” preceding a list with theconjunction “and” should not be treated as an exclusive list and shouldnot be construed as a list of categories with one item from eachcategory, unless specifically stated otherwise. A clause that recites“at least one of A, B, and C” can be infringed with only one of thelisted items, multiple of the listed items, and one or more of the itemsin the list and another item not listed. As used herein, the term “or”is inclusive unless otherwise explicitly noted. Thus, the phrase “atleast one of A, B, or C” is satisfied by any element from the set {A, B,C} or any combination thereof, including multiples of any element.

Embodiments of the systems, apparatus, methods, and techniques asdescribed herein may include the following embodiments.

Embodiment 1. A method comprising: determining, by a modem, a totalnumber of bits b_total required to be allocated over a set of availablefrequency channels configured as a discrete multi-tone (DMT) datacommunications format to enable telemetry communications between themodem and a logging tool while meeting requirements for a minimum totaltelemetry data rate and a maximum bit-error-rate (BER) for the telemetrycommunications; setting, by the modem, one or more proposedsignal-to-noise (SNR) margin values, each of the one or more proposedSNR margin values greater than a SNR minimum value, wherein the SNRminimum value is a minimum SNR value that may be untiled in the DMT datacommunications format while meeting the requirements for the minimumtotal telemetry data rate the maximum bit-error-rate (BER); and for eachof the one or more proposed SNR margin values, performing, by the modem,a bit allocation procedure to determine a number of bits that areallocatable over the set of available frequency channels based a currentsetting for the proposed SNR margin values, and determining, by themodem, whether the number of bits allocatable over the set of availablefrequency channels using the current setting for the proposed SNR marginvalue is greater than or equal to the total number of bits b_total.

Embodiment 2. The method of embodiment 1, wherein determining whetherthe number of bits allocatable is greater than or equal to the totalnumber of bits b_total further includes determining that the number ofbits allocatable based on the current setting for the proposed SNRmargin value is greater than or equal to the total number of bitsb_total, and formatting the telemetry communications to be performed aspart of a logging operation of a wellbore including providingcommunication signals between the modem and the logging tool using thebit allocations and the set of available frequency channels determinedto provide the number of bits greater than or equal to the total numberof bits b_total based on the current setting for the proposed SNRmargin.

Embodiment 3. The method of embodiments 1 or 2, wherein determiningwhether the number of bits allocatable is greater than or equal to thetotal number of bits b_total further includes determining that thenumber of bits allocatable based on the current setting for the proposedSNR margin value is less than the total number of bits b_total,iteratively lowering a current setting for the proposed SNR margin valueto one or more newly proposed SNR margin values, each of the one or morenewly proposed SNR margin values less than the current setting for theproposed SNR margin and greater than the SNR minimum value, and for eachof the iteratively lowered current setting for the proposed SNR marginvalues, performing, by the modem, a bit allocation procedure todetermine a number of bits that are allocatable over the set ofavailable frequency channels based iteratively lower current setting forthe proposed SNR margin values, and determining, by modem, whether thenumber of bits allocatable over the set of available frequency channelsusing the iteratively lowered current setting for the proposed SNRmargin value is greater than or equal to the total number of bitsb_total.

Embodiment 4. The method of embodiment 3, wherein iteratively loweringthe current setting for the proposed SNR margin value to a next one ofthe one or more newly proposed SNR margin values comprises lowering thecurrent setting for the proposed SNR margin value by a predeterminedamount to set the next one of the one or more newly proposed SNR marginvalues.

Embodiment 5. The method of embodiment 3, wherein iteratively loweringthe current setting for the proposed SNR margin value to a next one ofthe one or more newly proposed SNR margin values comprises lowering thecurrent setting for the proposed SNR margin value by an amount equal toa percentage of a difference between the current setting for the SNRmargin value and the SNR minimum value.

Embodiment 6. The method of any of embodiments 1 to 5, furthercomprising: determining that none of the proposed SNR margin valuesgreater than the SNR minimum value provides a telemetry communicationsformat that includes the number of bits allocatable over the set ofavailable frequency channels that is greater than or equal to the totalnumber of bits b_total, and outputting, by the modem, a warning messageincluding an indication that the total number of bits that may beallocated to the available frequency channels using any of the proposedSNR margin values can accommodate the total number of bits b_totalrequired number of bits being allocated over the available set offrequency channels while still meeting the requirements for the minimumtotal telemetry data rate and the maximum (BER).

Embodiment 7. The method of any of embodiments 1 to 6, furthercomprising: determining that none of the one or more proposedsignal-to-noise (SNR) margin values having value greater than the SNRminimum value provides a telemetry communications format that includesthe number of bits allocatable over the set of available frequencychannels that is greater than or equal to the total number of bitsb_total; automatically placing into a silent mode one or more devicesincluded in the logging tool; and formatting the telemetrycommunications to be performed as part of a logging operation of awellbore including providing communication signals between the modem andthe one or more devices of the logging tool that are not placed into thesilent more.

Embodiment 8. The method of any of embodiments 1 to 7, furthercomprising; receiving, at the modem, an input indicating that one ormore of the set of frequency channels are to be designated asunavailable, and that performing the bit allocation procedure todetermine a number of bits that are allocatable over the set ofavailable frequency channels comprises not allocating bits to thefrequency channels designated as being unavailable.

Embodiment 9, The method of any of embodiments 1 to 8, furthercomprising, receiving, by the modem, a tool string service profileincluding a data rate value for the minimum total telemetry data rate,and a BER value for the maximum bit-error-rate (BER) for the telemetrycommunications to be provided between the modem and the logging tool.

Embodiment 10. A system comprising; a downhole logging tool comprisingone or more sensors configured to perform sensing in a downholeenvironment of a borehole; a surface modem configured to communicativelycoupled to the logging tool, the surface modem comprising one or moreprocessors configured to set up and perform data communications betweenthe downhole tool and the surface modem while the logging tool isperforming a logging operation of the borehole; the one or moreprocessor configured to: determine a total number of bits b_totalrequired to be allocated over a set of available frequency channelsconfigured as a discrete multi-tone (DMT) communications format toenable telemetry communications between the modem and a logging toolwhile meeting requirements for a minimum total telemetry data rate and amaximum bit-error-rate (BER) for the telemetry communications; set oneor more proposed signal-to-noise (SNR) margin values, each of the one ormore proposed SNR margin values greater than a SNR minimum value,wherein the SNR minimum value is a minimum SNR value that may be untiledin the DMT data communications format while meeting the requirements forthe minimum total telemetry data rate the maximum bit-error-rate (BER);and for each of the one or more proposed SNR margin values, perform abit allocation procedure to determine a number of bits that areallocatable over the set of available frequency channels based a currentsetting for the proposed SNR margin values, and determining, by modem,whether the number of bits allocatable over the set of availablefrequency channels using the current setting for the proposed SNR marginvalue is greater than or equal to the total number of bits b_total.

Embodiment 11. The system of embodiment 10, wherein determining whetherthe number of bits allocatable is greater than or equal to the totalnumber of bits b_total further includes the one or more processorsconfigured to: determine that the number of bits allocatable based onthe current setting for the proposed SNR margin value is greater than orequal to the total number of bits b_total, and format the telemetrycommunications to be performed as part of a logging operation of awellbore including providing communication signals between the modem andthe logging tool using the bit allocations and the set of availablefrequency channels determined to provide the number of bits greater thanor equal to the total number of bits b_total based on the currentsetting for the proposed SNR margin.

Embodiment 12. The system of embodiment 10, wherein determining whetherthe number of bits allocatable is greater than or equal to the totalnumber of bits b_total further includes the one or more processorsfurther configured to: determine that the number of bits allocatablebased on the current setting for the proposed SNR margin value is lessthan the total number of bits b_total, iteratively lowering the currentsetting for the proposed SNR margin value to one or more newly proposedSNR margin values, each of the one or more newly proposed SNR marginvalues less than the current setting for the proposed SNR margin andgreater than the SNR minimum value, and for each of the iterativelylower current setting for the proposed SNR margin values, perform a bitallocation procedure to determine a number of bits that are allocatableover the set of available frequency channels based iteratively lowercurrent setting for the proposed SNR margin values, and determining, bymodem, whether the number of bits allocatable over the set of availablefrequency channels using the iteratively lowered current setting for theproposed SNR margin value is greater than or equal to the total numberof bits b_total.

Embodiment 13. The system of embodiment 12, wherein iteratively loweringthe current setting for the proposed SNR margin value to a next one ofthe one or more newly proposed SNR margin values comprises lowering thecurrent setting for the proposed SNR margin value by a predeterminedamount to set the next one of the one or more newly proposed SNR marginvalues.

Embodiment 14. The system of embodiment 12, wherein iteratively loweringthe current setting for the proposed SNR margin value to a next one ofthe one or more newly proposed SNR margin values comprises lowering thecurrent setting for the proposed SNR margin value by an amount equal toa percentage of a difference between the current setting for the SNRmargin value and the SNR minimum value.

Embodiment 15. The system of embodiment 12, further including the one ormore processors configured to: determine that none of the proposed SNRmargin values greater than the SNR minimum value provides a telemetrycommunications format that includes the number of bits allocatable overthe set of available frequency channels that is greater than or equal tothe total number of bits b_total, and output a warning message includingan indication that the total number of bits that may be allocated to theavailable frequency channels using any of the proposed SNR margin valuescan accommodate the total number of bits b_total being allocated overthe available set of frequency channels while still meeting therequirements for the minimum total telemetry data rate and the maximum(BER).

Embodiment 16. The system of any of embodiments 10 to 15, furtherincluding the one or more processors configured to: determine that noneof the one or more proposed signal-to-noise (SNR) margin values havingvalue greater than the SNR minimum value provides a telemetrycommunications format that includes the number of bits allocatable overthe set of available frequency channels that is greater than or equal tothe total number of bits b_total; automatically placing into a silentmode one or more devices included in the logging tool; and format thetelemetry communications to be performed as part of a logging operationof a wellbore including providing communication signals between themodem and the one or more devices of the logging tool that are notplaced into the silent more.

Embodiment 17. The system of embodiment 16, wherein at least one of thelogging tools comprises a High-Fidelity Borehole Imager configured toprovide information related to a micro-resistivity associated with aborehole environment.

Embodiment 18. A non-transitory, computer-readable medium havinginstructions stored thereon that are executable by a processor of acomputing device to perform operations comprising: determining a totalnumber of bits b_total required to be allocated over a set of availablefrequency channels configured as a discrete multi-tone (DMT)communications format to enable telemetry communications between a modemand a logging tool while meeting requirements for a minimum totaltelemetry data rate and a maximum bit-error-rate (BER) for the telemetrycommunications; setting one or more proposed signal-to-noise (SNR)margin values, each of the one or more proposed SNR margin valuesgreater than a SNR minimum value, wherein the SNR minimum value is aminimum SNR value that may be untiled in the DMT data communicationsformat while meeting the requirements for the minimum total telemetrydata rate the maximum bit-error-rate (BER); and for each of the one ormore proposed SNR margin values, performing a bit allocation procedureto determine a number of bits that are allocatable over the set ofavailable frequency channels based a current setting for the proposedSNR margin values, and determining, by modem, whether the number of bitsallocatable over the set of available frequency channels using thecurrent setting for the proposed SNR margin value is greater than orequal to the total number of bits b_total.

Embodiment 19. The non-transitory, computer-readable medium ofembodiment 18, having instructions stored thereon that are executable bya processor of a computing device to perform operations furthercomprising: determining whether the number of bits allocatable isgreater than or equal to the total number of bits b_total, includesdetermining that the number of bits allocatable based on the currentsetting for the proposed SNR margin value is greater than or equal tothe total number of bits b_total, and formatting the telemetrycommunications to be performed as part of a logging operation of awellbore including providing communication signals between the modem andthe logging tool using the bit allocations and the set of availablefrequency channels determined to provide the number of bits greater thanor equal to the total number of bits b_total based on the currentsetting for the proposed SNR margin.

Embodiment 20. The non-transitory, computer-readable medium ofembodiment 18, wherein determining whether the number of bitsallocatable is greater than or equal to the total number of bits b_totalfurther includes: determining that the number of bits allocatable basedon the current setting for the proposed SNR margin value is less thanthe total number of bits b_total, iteratively lower the current settingfor the proposed SNR margin value to one or more newly proposed SNRmargin values, each of the one or more newly proposed SNR margin valuesless than the current setting for the proposed SNR margin and greaterthan the SNR minimum value, and for each of the iteratively loweredcurrent settings for the proposed SNR margin values, performing, by themodem, a bit allocation procedure to determine a number of bits that areallocatable over the set of available frequency channels basediteratively lower current setting for the proposed SNR margin values,and determining, by modem, whether the number of bits allocatable overthe set of available frequency channels using the iteratively loweredcurrent setting for the proposed SNR margin value is greater than orequal to the total number of bits b_total.

What is claimed is:
 1. A method comprising: determining, by a modem, atotal number of bits b_total required to be allocated over a set ofavailable frequency channels configured as a discrete multi-tone (DMT)data communications format to enable telemetry communications betweenthe modem and a logging tool while meeting requirements for a minimumtotal telemetry data rate and a maximum bit-error-rate (BER) for thetelemetry communications; setting, by the modem, one or more proposedsignal-to-noise (SNR) margin values, each of the one or more proposedSNR margin values greater than a SNR minimum value, wherein the SNRminimum value is a minimum SNR value that may be untiled in the DMT datacommunications format while meeting the requirements for the minimumtotal telemetry data rate the maximum bit-error-rate (BER); and for eachof the one or more proposed SNR margin values, performing, by the modem,a bit allocation procedure to determine a number of bits that areallocatable over the set of available frequency channels based a currentsetting for the proposed SNR margin values, and determining, by themodem, whether the number of bits allocatable over the set of availablefrequency channels using the current setting for the proposed SNR marginvalue is greater than or equal to the total number of bits b_total. 2.The method of claim 1, wherein determining whether the number of bitsallocatable is greater than or equal to the total number of bits b_totalfurther includes determining that the number of bits allocatable basedon the current setting for the proposed SNR margin value is greater thanor equal to the total number of bits b_total, and formatting thetelemetry communications to be performed as part of a logging operationof a wellbore including providing communication signals between themodem and the logging tool using the bit allocations and the set ofavailable frequency channels determined to provide the number of bitsgreater than or equal to the total number of bits b_total based on thecurrent setting for the proposed SNR margin.
 3. The method of claim 1,wherein determining whether the number of bits allocatable is greaterthan or equal to the total number of bits b_total further includesdetermining that the number of bits allocatable based on the currentsetting for the proposed SNR margin value is less than the total numberof bits b_total, iteratively lowering a current setting for the proposedSNR margin value to one or more newly proposed SNR margin values, eachof the one or more newly proposed SNR margin values less than thecurrent setting for the proposed SNR margin and greater than the SNRminimum value, and for each of the iteratively lowered current settingfor the proposed SNR margin values, performing, by the modem, a bitallocation procedure to determine a number of bits that are allocatableover the set of available frequency channels based iteratively lowercurrent setting for the proposed SNR margin values, and determining, bymodem, whether the number of bits allocatable over the set of availablefrequency channels using the iteratively lowered current setting for theproposed SNR margin value is greater than or equal to the total numberof bits b_total.
 4. The method of claim 3, wherein iteratively loweringthe current setting for the proposed SNR margin value to a next one ofthe one or more newly proposed SNR margin values comprises lowering thecurrent setting for the proposed SNR margin value by a predeterminedamount to set the next one of the one or more newly proposed SNR marginvalues.
 5. The method of claim 3, wherein iteratively lowering thecurrent setting for the proposed SNR margin value to a next one of theone or more newly proposed SNR margin values comprises lowering thecurrent setting for the proposed SNR margin value by an amount equal toa percentage of a difference between the current setting for the SNRmargin value and the SNR minimum value.
 6. The method of claim 3,further comprising: determining that none of the proposed SNR marginvalues greater than the SNR minimum value provides a telemetrycommunications format that includes the number of bits allocatable overthe set of available frequency channels that is greater than or equal tothe total number of bits b_total, and outputting, by the modem, awarning message including an indication that the total number of bitsthat may be allocated to the available frequency channels using any ofthe proposed SNR margin values can accommodate the total number of bitsb_total required number of bits being allocated over the available setof frequency channels while still meeting the requirements for theminimum total telemetry data rate and the maximum (BER).
 7. The methodof claim 1, further comprising: determining that none of the one or moreproposed signal-to-noise (SNR) margin values having value greater thanthe SNR minimum value provides a telemetry communications format thatincludes the number of bits allocatable over the set of availablefrequency channels that is greater than or equal to the total number ofbits b_total; automatically placing into a silent mode one or moredevices included in the logging tool; and formatting the telemetrycommunications to be performed as part of a logging operation of awellbore including providing communication signals between the modem andthe one or more devices of the logging tool that are not placed into thesilent more.
 8. The method of claim 1, further comprising; receiving, atthe modem, an input indicating that one or more of the set of frequencychannels are to be designated as unavailable, and that performing thebit allocation procedure to determine a number of bits that areallocatable over the set of available frequency channels comprises notallocating bits to the frequency channels designated as beingunavailable.
 9. The method of claim 1, further comprising, receiving, bythe modem, a tool string service profile including a data rate value forthe minimum total telemetry data rate, and a BER value for the maximumbit-error-rate (BER) for the telemetry communications to be providedbetween the modem and the logging tool.
 10. A system comprising; adownhole logging tool comprising one or more sensors configured toperform sensing in a downhole environment of a borehole; a surface modemconfigured to communicatively coupled to the logging tool, the surfacemodem comprising one or more processors configured to set up and performdata communications between the downhole tool and the surface modemwhile the logging tool is performing a logging operation of theborehole; the one or more processor configured to: determine a totalnumber of bits b_total required to be allocated over a set of availablefrequency channels configured as a discrete multi-tone (DMT)communications format to enable telemetry communications between themodem and a logging tool while meeting requirements for a minimum totaltelemetry data rate and a maximum bit-error-rate (BER) for the telemetrycommunications; set one or more proposed signal-to-noise (SNR) marginvalues, each of the one or more proposed SNR margin values greater thana SNR minimum value, wherein the SNR minimum value is a minimum SNRvalue that may be untiled in the DMT data communications format whilemeeting the requirements for the minimum total telemetry data rate themaximum bit-error-rate (BER); and for each of the one or more proposedSNR margin values, perform a bit allocation procedure to determine anumber of bits that are allocatable over the set of available frequencychannels based a current setting for the proposed SNR margin values, anddetermining, by modem, whether the number of bits allocatable over theset of available frequency channels using the current setting for theproposed SNR margin value is greater than or equal to the total numberof bits b_total.
 11. The system of claim 10, wherein determining whetherthe number of bits allocatable is greater than or equal to the totalnumber of bits b_total further includes the one or more processorsconfigured to: determine that the number of bits allocatable based onthe current setting for the proposed SNR margin value is greater than orequal to the total number of bits b_total, and format the telemetrycommunications to be performed as part of a logging operation of awellbore including providing communication signals between the modem andthe logging tool using the bit allocations and the set of availablefrequency channels determined to provide the number of bits greater thanor equal to the total number of bits b_total based on the currentsetting for the proposed SNR margin.
 12. The system of claim 10, whereindetermining whether the number of bits allocatable is greater than orequal to the total number of bits b_total further includes the one ormore processors further configured to: determine that the number of bitsallocatable based on the current setting for the proposed SNR marginvalue is less than the total number of bits b_total, iterativelylowering the current setting for the proposed SNR margin value to one ormore newly proposed SNR margin values, each of the one or more newlyproposed SNR margin values less than the current setting for theproposed SNR margin and greater than the SNR minimum value, and for eachof the iteratively lower current setting for the proposed SNR marginvalues, perform a bit allocation procedure to determine a number of bitsthat are allocatable over the set of available frequency channels basediteratively lower current setting for the proposed SNR margin values,and determining, by modem, whether the number of bits allocatable overthe set of available frequency channels using the iteratively loweredcurrent setting for the proposed SNR margin value is greater than orequal to the total number of bits b_total.
 13. The system of claim 12,wherein iteratively lowering the current setting for the proposed SNRmargin value to a next one of the one or more newly proposed SNR marginvalues comprises lowering the current setting for the proposed SNRmargin value by a predetermined amount to set the next one of the one ormore newly proposed SNR margin values.
 14. The system of claim 12,wherein iteratively lowering the current setting for the proposed SNRmargin value to a next one of the one or more newly proposed SNR marginvalues comprises lowering the current setting for the proposed SNRmargin value by an amount equal to a percentage of a difference betweenthe current setting for the SNR margin value and the SNR minimum value.15. The system of claim 12, further including the one or more processorsconfigured to: determine that none of the proposed SNR margin valuesgreater than the SNR minimum value provides a telemetry communicationsformat that includes the number of bits allocatable over the set ofavailable frequency channels that is greater than or equal to the totalnumber of bits b_total, and output a warning message including anindication that the total number of bits that may be allocated to theavailable frequency channels using any of the proposed SNR margin valuescan accommodate the total number of bits b_total being allocated overthe available set of frequency channels while still meeting therequirements for the minimum total telemetry data rate and the maximum(BER).
 16. The system of claim 10, further including the one or moreprocessors configured to: determine that none of the one or moreproposed signal-to-noise (SNR) margin values having value greater thanthe SNR minimum value provides a telemetry communications format thatincludes the number of bits allocatable over the set of availablefrequency channels that is greater than or equal to the total number ofbits b_total; automatically placing into a silent mode one or moredevices included in the logging tool; and format the telemetrycommunications to be performed as part of a logging operation of awellbore including providing communication signals between the modem andthe one or more devices of the logging tool that are not placed into thesilent more.
 17. The system of claim 16, wherein at least one of thelogging tools comprises a High-Fidelity Borehole Imager configured toprovide information related to a micro-resistivity associated with aborehole environment.
 18. A non-transitory, computer-readable mediumhaving instructions stored thereon that are executable by a processor ofa computing device to perform operations comprising: determining a totalnumber of bits b_total required to be allocated over a set of availablefrequency channels configured as a discrete multi-tone (DMT)communications format to enable telemetry communications between a modemand a logging tool while meeting requirements for a minimum totaltelemetry data rate and a maximum bit-error-rate (BER) for the telemetrycommunications; setting one or more proposed signal-to-noise (SNR)margin values, each of the one or more proposed SNR margin valuesgreater than a SNR minimum value, wherein the SNR minimum value is aminimum SNR value that may be untiled in the DMT data communicationsformat while meeting the requirements for the minimum total telemetrydata rate the maximum bit-error-rate (BER); and for each of the one ormore proposed SNR margin values, performing a bit allocation procedureto determine a number of bits that are allocatable over the set ofavailable frequency channels based a current setting for the proposedSNR margin values, and determining, by modem, whether the number of bitsallocatable over the set of available frequency channels using thecurrent setting for the proposed SNR margin value is greater than orequal to the total number of bits b_total.
 19. The non-transitory,computer-readable medium of claim 18, having instructions stored thereonthat are executable by a processor of a computing device to performoperations further comprising: determining whether the number of bitsallocatable is greater than or equal to the total number of bitsb_total, includes determining that the number of bits allocatable basedon the current setting for the proposed SNR margin value is greater thanor equal to the total number of bits b_total, and formatting thetelemetry communications to be performed as part of a logging operationof a wellbore including providing communication signals between themodem and the logging tool using the bit allocations and the set ofavailable frequency channels determined to provide the number of bitsgreater than or equal to the total number of bits b_total based on thecurrent setting for the proposed SNR margin.
 20. The non-transitory,computer-readable medium of claim 18, wherein determining whether thenumber of bits allocatable is greater than or equal to the total numberof bits b_total further includes: determining that the number of bitsallocatable based on the current setting for the proposed SNR marginvalue is less than the total number of bits b_total, iteratively lowerthe current setting for the proposed SNR margin value to one or morenewly proposed SNR margin values, each of the one or more newly proposedSNR margin values less than the current setting for the proposed SNRmargin and greater than the SNR minimum value, and for each of theiteratively lowered current settings for the proposed SNR margin values,performing, by the modem, a bit allocation procedure to determine anumber of bits that are allocatable over the set of available frequencychannels based iteratively lower current setting for the proposed SNRmargin values, and determining, by modem, whether the number of bitsallocatable over the set of available frequency channels using theiteratively lowered current setting for the proposed SNR margin value isgreater than or equal to the total number of bits b_total.